Merge fixups from Thomas Waldmann

33 files changed, 65 insertions, 118 deletions

diff --git a/NEWS b/NEWS
index 53280dc4..c0a1755b 100644
--- a/NEWS
+++ b/NEWS
@@ -450,7 +450,7 @@ Bug fixes:
   by ROGERIO DE CARVALHO BASTOS and patched by Peter Valdemar Mørch.
 * Setuid and setgid bits are now restored correctly, when restore happens
   as root. Reported by Pavel Kokolemin.
-* Obnam now complains if no backup roots have been specfied.
+* Obnam now complains if no backup roots have been specified.
 
 Version 1.2, released 2012-10-06
 --------------------------------
diff --git a/find-all-obnam-errors b/find-all-obnam-errors
index c0403dd4..711f1f8c 100755
--- a/find-all-obnam-errors
+++ b/find-all-obnam-errors
@@ -17,7 +17,6 @@
 # =*= License: GPL-3+ =*=
 
 
-import collections
 import imp
 import inspect
 import os
diff --git a/metadata-speed b/metadata-speed
index c821bf46..b183a4b9 100755
--- a/metadata-speed
+++ b/metadata-speed
@@ -15,9 +15,6 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
-import os
-import random
-import shutil
 import sys
 import time
 
diff --git a/obnam-benchmark b/obnam-benchmark
index 0b54c612..05e62b3b 100755
--- a/obnam-benchmark
+++ b/obnam-benchmark
@@ -23,7 +23,6 @@ import platform
 import re
 import shutil
 import stat
-import sys
 import tempfile
 import time
 
diff --git a/obnamlib/app.py b/obnamlib/app.py
index a3159acc..476259ae 100644
--- a/obnamlib/app.py
+++ b/obnamlib/app.py
@@ -17,9 +17,7 @@
 import cliapp
 import larch
 import logging
-import os
 import socket
-import StringIO
 import sys
 import time
 import tracing
@@ -85,7 +83,7 @@ class App(cliapp.Application):
             metavar='TIMEOUT',
             default=60)
 
-        # Repositofy format selection.
+        # Repository format selection.
 
         self.settings.choice(
             ['repository-format'],
diff --git a/obnamlib/encryption.py b/obnamlib/encryption.py
index 775e008a..ddd50fd7 100644
--- a/obnamlib/encryption.py
+++ b/obnamlib/encryption.py
@@ -38,9 +38,9 @@ def generate_symmetric_key(numbits, filename='/dev/random'):
 
     tracing.trace('numbits=%d', numbits)
 
-    bytes = (numbits + 7) / 8
+    count = (numbits + 7) / 8
     f = open(filename, 'rb')
-    key = f.read(bytes)
+    key = f.read(count)
     f.close()
 
     return key.encode('hex')
diff --git a/obnamlib/encryption_tests.py b/obnamlib/encryption_tests.py
index 0cf58394..7781be43 100644
--- a/obnamlib/encryption_tests.py
+++ b/obnamlib/encryption_tests.py
@@ -16,7 +16,6 @@
 
 import os
 import shutil
-import subprocess
 import tempfile
 import unittest
 
diff --git a/obnamlib/fmt_6/chunklist.py b/obnamlib/fmt_6/chunklist.py
index e34aa652..f94d83cf 100644
--- a/obnamlib/fmt_6/chunklist.py
+++ b/obnamlib/fmt_6/chunklist.py
@@ -14,9 +14,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
-import hashlib
 import struct
-import random
 import tracing
 
 import obnamlib
diff --git a/obnamlib/fmt_6/clientmetadatatree.py b/obnamlib/fmt_6/clientmetadatatree.py
index a652fb44..ac977504 100644
--- a/obnamlib/fmt_6/clientmetadatatree.py
+++ b/obnamlib/fmt_6/clientmetadatatree.py
@@ -88,11 +88,11 @@ class ClientMetadataTree(obnamlib.RepositoryTree):
     def default_file_id(self, filename):
         '''Return hash of filename suitable for use as main key.'''
         tracing.trace(repr(filename))
-        def hash(s):
+        def shorthash(s):
             return hashlib.md5(s).digest()[:4]
         dirname = os.path.dirname(filename)
         basename = os.path.basename(filename)
-        return hash(dirname) + hash(basename)
+        return shorthash(dirname) + shorthash(basename)
 
     def _bad_default_file_id(self, filename):
         '''For use by unit tests.'''
diff --git a/obnamlib/fmt_6/clientmetadatatree_tests.py b/obnamlib/fmt_6/clientmetadatatree_tests.py
index 8576bdd9..32913204 100644
--- a/obnamlib/fmt_6/clientmetadatatree_tests.py
+++ b/obnamlib/fmt_6/clientmetadatatree_tests.py
@@ -270,23 +270,6 @@ class ClientMetadataTreeFileOpsTests(unittest.TestCase):
         self.assertEqual(list(self.client.tree.lookup_range(minkey, maxkey)),
                          [])
 
-    def test_generation_has_no_chunk_refs_initially(self):
-        minkey = self.client.chunk_key(0, 0)
-        maxkey = self.client.chunk_key(obnamlib.MAX_ID, obnamlib.MAX_ID)
-        self.assertEqual(list(self.client.tree.lookup_range(minkey, maxkey)),
-                         [])
-
-    def test_sets_file_chunks(self):
-        self.client.set_file_chunks('/foo', [1, 2, 3])
-        self.assertEqual(self.client.get_file_chunks(self.clientid, '/foo'),
-                         [1, 2, 3])
-
-    def test_generation_has_no_chunk_refs_initially(self):
-        minkey = self.client.chunk_key(0, 0)
-        maxkey = self.client.chunk_key(obnamlib.MAX_ID, obnamlib.MAX_ID)
-        self.assertEqual(list(self.client.tree.lookup_range(minkey, maxkey)),
-                         [])
-
     def test_set_file_chunks_adds_chunk_refs(self):
         self.client.set_file_chunks('/foo', [1, 2])
         file_id = self.client.get_file_id(self.client.tree, '/foo')
diff --git a/obnamlib/fmt_6/metadata_codec.py b/obnamlib/fmt_6/metadata_codec.py
index 2e281c6b..55405d55 100644
--- a/obnamlib/fmt_6/metadata_codec.py
+++ b/obnamlib/fmt_6/metadata_codec.py
@@ -14,6 +14,7 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
+import logging
 import struct
 
 import obnamlib
diff --git a/obnamlib/fmt_6/repo_fmt_6.py b/obnamlib/fmt_6/repo_fmt_6.py
index 7a938c50..9f94ad4e 100644
--- a/obnamlib/fmt_6/repo_fmt_6.py
+++ b/obnamlib/fmt_6/repo_fmt_6.py
@@ -22,7 +22,6 @@ import os
 import random
 import re
 import stat
-import struct
 import time
 import tracing
 
@@ -555,7 +554,7 @@ class RepositoryFormat6(obnamlib.RepositoryInterface):
 
     def set_generation_key(
         self, generation_id, key, value): # pragma: no cover
-        # FIXME: This no worky for generations other than the currently
+        # FIXME: This is not working for generations other than the currently
         # started one. There should at least be an assert about it.
 
         client_name, gen_number = self._unpack_gen_id(generation_id)
@@ -882,7 +881,7 @@ class RepositoryFormat6(obnamlib.RepositoryInterface):
         try:
             expected_checksum = self._chunklist.get_checksum(chunk_id)
         except KeyError: # pragma: no cover
-            # Chunk is not in the checksum tree, so we cannot valide
+            # Chunk is not in the checksum tree, so we cannot validate
             # its checksum. We'll just assume it's OK.
             return True
         return actual_checksum == expected_checksum
diff --git a/obnamlib/fmt_6/repo_tree.py b/obnamlib/fmt_6/repo_tree.py
index 64302f5a..bd755074 100644
--- a/obnamlib/fmt_6/repo_tree.py
+++ b/obnamlib/fmt_6/repo_tree.py
@@ -17,8 +17,6 @@
 import larch
 import tracing
 
-import obnamlib
-
 
 class RepositoryTree(object):
 
diff --git a/obnamlib/fmt_simple/simple.py b/obnamlib/fmt_simple/simple.py
index 7651ca0a..bc6f996a 100644
--- a/obnamlib/fmt_simple/simple.py
+++ b/obnamlib/fmt_simple/simple.py
@@ -18,6 +18,7 @@
 
 import copy
 import hashlib
+import errno
 import os
 import random
 import StringIO
@@ -419,11 +420,11 @@ class SimpleClient(SimpleToplevel):
         generations = self._data.get('generations', [])
         ids = [int(gen['id']) for gen in generations]
         if ids:
-            newest = ids[-1]
-            next = newest + 1
+            newest_id = ids[-1]
+            next_id = newest_id + 1
         else:
-            next = 1
-        return str(next)
+            next_id = 1
+        return str(next_id)
 
     def remove_generation(self, gen_number):
         self._require_lock()
diff --git a/obnamlib/metadata_tests.py b/obnamlib/metadata_tests.py
index 98fbebe7..34afe602 100644
--- a/obnamlib/metadata_tests.py
+++ b/obnamlib/metadata_tests.py
@@ -18,7 +18,6 @@ import os
 import stat
 import tempfile
 import unittest
-import platform
 
 import obnamlib
 
diff --git a/obnamlib/pluginbase.py b/obnamlib/pluginbase.py
index d1a75fb4..0e8916f5 100644
--- a/obnamlib/pluginbase.py
+++ b/obnamlib/pluginbase.py
@@ -16,8 +16,6 @@
 
 import cliapp
 
-import obnamlib
-
 
 class ObnamPlugin(cliapp.Plugin):
 
diff --git a/obnamlib/plugins/backup_plugin.py b/obnamlib/plugins/backup_plugin.py
index 6c63955a..cbc9f237 100644
--- a/obnamlib/plugins/backup_plugin.py
+++ b/obnamlib/plugins/backup_plugin.py
@@ -15,17 +15,14 @@
 
 
 import errno
-import gc
 import hashlib
 import logging
 import os
 import re
 import stat
-import sys
 import time
 import traceback
 import tracing
-import ttystatus
 
 import obnamlib
 import larch
@@ -1016,7 +1013,7 @@ class BackupPlugin(obnamlib.ObnamPlugin):
                 self.repo.append_file_chunk_id(
                     self.new_generation, filename, chunk_id)
             else:
-                self.self.update_progress_with_upload(len(data))
+                self.progress.update_progress_with_upload(len(data))
 
             if not self.pretend and self.time_for_checkpoint():
                 logging.debug('making checkpoint in the middle of a file')
diff --git a/obnamlib/plugins/compression_plugin.py b/obnamlib/plugins/compression_plugin.py
index 54f08566..9f0d8b68 100644
--- a/obnamlib/plugins/compression_plugin.py
+++ b/obnamlib/plugins/compression_plugin.py
@@ -15,7 +15,6 @@
 
 
 import logging
-import os
 import zlib
 
 import obnamlib
diff --git a/obnamlib/plugins/force_lock_plugin.py b/obnamlib/plugins/force_lock_plugin.py
index 931a96fc..5eaf7be3 100644
--- a/obnamlib/plugins/force_lock_plugin.py
+++ b/obnamlib/plugins/force_lock_plugin.py
@@ -15,7 +15,6 @@
 
 
 import logging
-import os
 
 import obnamlib
 
diff --git a/obnamlib/plugins/fsck_plugin.py b/obnamlib/plugins/fsck_plugin.py
index 86c7ea9b..5b9c4a64 100644
--- a/obnamlib/plugins/fsck_plugin.py
+++ b/obnamlib/plugins/fsck_plugin.py
@@ -15,12 +15,9 @@
 
 
 import hashlib
-import larch.fsck
 import logging
-import os
 import stat
 import sys
-import ttystatus
 
 import obnamlib
 from obnamlib import WorkItem
diff --git a/obnamlib/plugins/fuse_plugin.py b/obnamlib/plugins/fuse_plugin.py
index 30531295..f438feb7 100644
--- a/obnamlib/plugins/fuse_plugin.py
+++ b/obnamlib/plugins/fuse_plugin.py
@@ -16,7 +16,6 @@
 
 import os
 import stat
-import sys
 import logging
 import errno
 import struct
@@ -419,7 +418,7 @@ class ObnamFuse(fuse.Fuse):
         stv = fuse.StatVfs()
         stv.f_bsize   = 65536
         stv.f_frsize  = 0
-        stv.f_blocks  = blocks/65536
+        stv.f_blocks  = total_data / 65536
         stv.f_bfree   = 0
         stv.f_bavail  = 0
         stv.f_files   = files
@@ -555,7 +554,7 @@ class MountPlugin(obnamlib.ObnamPlugin):
 
     '''Mount backup repository as a user-space filesystem.
 
-    At the momemnt only a specific generation can be mounted
+    At the moment only a specific generation can be mounted
 
     '''
 
diff --git a/obnamlib/plugins/restore_plugin.py b/obnamlib/plugins/restore_plugin.py
index 7d54f412..88ea15b7 100644
--- a/obnamlib/plugins/restore_plugin.py
+++ b/obnamlib/plugins/restore_plugin.py
@@ -19,7 +19,6 @@ import logging
 import os
 import stat
 import time
-import ttystatus
 
 import obnamlib
 
diff --git a/obnamlib/plugins/sftp_plugin.py b/obnamlib/plugins/sftp_plugin.py
index 6329e520..59d83ecd 100644
--- a/obnamlib/plugins/sftp_plugin.py
+++ b/obnamlib/plugins/sftp_plugin.py
@@ -25,8 +25,8 @@ import socket
 import stat
 import subprocess
 import time
-import traceback
 import urlparse
+import getpass
 
 
 # As of 2010-07-10, Debian's paramiko package triggers
@@ -244,12 +244,9 @@ class SftpFS(obnamlib.VirtualFileSystem):
         return True
 
     def _connect_paramiko(self):
+        remote = (self.host, self.port or 22)
         logging.debug(
-            'connect_paramiko: host=%s port=%s' % (self.host, self.port))
-        if self.port:
-            remote = (self.host, self.port)
-        else:
-            remote = (self.host)
+            'connect_paramiko: host=%s port=%s' % remote)
         self.transport = paramiko.Transport(remote)
         self.transport.connect()
         logging.debug('connect_paramiko: connected')
@@ -591,8 +588,9 @@ class SftpFS(obnamlib.VirtualFileSystem):
 
     @ioerror_to_oserror
     def write_file(self, pathname, contents):
+        mode = 'wbx'
         try:
-            f = self.open(pathname, 'wbx')
+            f = self.open(pathname, mode)
         except (IOError, OSError), e:
             # When the path to the file to be written does not
             # exist, we try to create the directories below. Note that
@@ -604,7 +602,7 @@ class SftpFS(obnamlib.VirtualFileSystem):
                 raise
             dirname = os.path.dirname(pathname)
             self.makedirs(dirname)
-            f = self.open(pathname, 'wx')
+            f = self.open(pathname, mode)
 
         self._write_helper(f, contents)
         f.close()
diff --git a/obnamlib/plugins/show_plugin.py b/obnamlib/plugins/show_plugin.py
index 00d478d4..a15c10a5 100644
--- a/obnamlib/plugins/show_plugin.py
+++ b/obnamlib/plugins/show_plugin.py
@@ -14,7 +14,6 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
-import os
 import re
 import stat
 import sys
@@ -159,12 +158,12 @@ class ShowPlugin(obnamlib.ObnamPlugin):
             # the repository is empty / the client does not exist
             self.app.output.write('CRITICAL: no backup found.\n')
             sys.exit(2)
-        elif (now - most_recent > critical_age):
+        elif now - most_recent > critical_age:
             self.app.output.write(
                 'CRITICAL: backup is old.  last backup was %s.\n' %
                     (self.format_time(most_recent)))
             sys.exit(2)
-        elif (now - most_recent > warn_age):
+        elif now - most_recent > warn_age:
             self.app.output.write(
                 'WARNING: backup is old.  last backup was %s.\n' %
                     self.format_time(most_recent))
@@ -200,9 +199,9 @@ class ShowPlugin(obnamlib.ObnamPlugin):
             ended = self.format_time(ended)
             hdr('Generation %s (%s - %s)\n' %
                 (self.repo.make_generation_spec(gen_id), started, ended))
-            for file in args:
-                file = self.remove_trailing_slashes(file)
-                self.show_objects(cb, gen_id, file)
+            for filename in args:
+                filename = self.remove_trailing_slashes(filename)
+                self.show_objects(cb, gen_id, filename)
 
         self.repo.close()
 
@@ -291,7 +290,7 @@ class ShowPlugin(obnamlib.ObnamPlugin):
         enc_filename = enc_filename.replace(" ", "%20")
         enc_filename = enc_filename.replace("\t", "%09")
 
-        if (filename == "/"): return
+        if filename == "/": return
 
         self.app.output.write("%s%s\t%d\t%#x\n" %
             (mode_str, enc_filename, size, mtime_sec))
@@ -309,7 +308,7 @@ class ShowPlugin(obnamlib.ObnamPlugin):
 
         if self.app.settings['verbose']:
             sys.stdout.write('%s ' % change_char)
-            self.show_item(gen_id, fullname)
+            self.show_item_ls(gen_id, fullname)
         else:
             self.app.output.write('%s %s\n' % (change_char, fullname))
 
@@ -449,10 +448,6 @@ class ShowPlugin(obnamlib.ObnamPlugin):
                  timestamp,
                  name)
 
-    def format(self, fields):
-        return ' '. join(self.align(widths[i], fields[i], i)
-                          for i in range(len(fields)))
-
     def align(self, width, field, field_no):
         if field_no in self.leftists:
             return '%-*s' % (width, field)
diff --git a/obnamlib/plugins/vfs_local_plugin.py b/obnamlib/plugins/vfs_local_plugin.py
index 2851c5d6..d72ac91a 100644
--- a/obnamlib/plugins/vfs_local_plugin.py
+++ b/obnamlib/plugins/vfs_local_plugin.py
@@ -15,9 +15,6 @@
 
 
 import logging
-import os
-import re
-import stat
 
 import obnamlib
 
diff --git a/obnamlib/repo_dummy.py b/obnamlib/repo_dummy.py
index 3263a216..09664fee 100644
--- a/obnamlib/repo_dummy.py
+++ b/obnamlib/repo_dummy.py
@@ -222,7 +222,7 @@ class DummyClient(object):
         return ('file', gen_id, filename)
 
     def _is_filekey(self, key):
-        return (type(key) is tuple and len(key) == 3 and key[0] == 'file')
+        return type(key) is tuple and len(key) == 3 and key[0] == 'file'
 
     def file_exists(self, gen_id, filename):
         return self.data.get_value(self._filekey(gen_id, filename), False)
@@ -248,7 +248,7 @@ class DummyClient(object):
         return ('filekey', gen_id, filename, key)
 
     def _is_filekeykey(self, key):
-        return (type(key) is tuple and len(key) == 4 and key[0] == 'filekey')
+        return type(key) is tuple and len(key) == 4 and key[0] == 'filekey'
 
     def _require_file(self, gen_id, filename):
         if not self.file_exists(gen_id, filename):
diff --git a/obnamlib/repo_interface.py b/obnamlib/repo_interface.py
index 6b5c2a20..b39f8abe 100644
--- a/obnamlib/repo_interface.py
+++ b/obnamlib/repo_interface.py
@@ -28,7 +28,7 @@ import obnamlib
 # The following is a canonical list of all keys that can be used with
 # the repository interface for key/value pairs. Not all formats need
 # to support all keys, but they all must support the test keys, for
-# the test suite to function. All commong file metadata keys must also
+# the test suite to function. All common file metadata keys must also
 # be supported by all formats.
 #
 # The keys may change in value from run to run. Treat them as opaque,
@@ -239,7 +239,7 @@ class RepositoryInterface(object):
     implementation with the ``set_fs`` method.
 
     It must be stressed that ALL access to the repository go via
-    an implemention of RepositoryInterface. Further, all the
+    an implementation of RepositoryInterface. Further, all the
     implementation classes must be instantiated via RepositoryFactory.
 
     The abstraction RepositoryInterface provides for repositories
@@ -479,7 +479,7 @@ class RepositoryInterface(object):
         raise NotImplementedError()
 
     def get_client_generation_ids(self, client_name):
-        '''Return a list of opague ids for generations in a client.
+        '''Return a list of opaque ids for generations in a client.
 
         The list is ordered: the first id in the list is the oldest
         generation. The ids needs not be sortable, and they may or
@@ -712,7 +712,7 @@ class RepositoryInterface(object):
         '''Have we got the chunk index lock?'''
         raise NotImplementedError()
 
-    def force_chunk_indexex_lock(self):
+    def force_chunk_indexes_lock(self):
         '''Forces a chunk index lock open.'''
         raise NotImplementedError()
 
@@ -801,7 +801,7 @@ class RepositoryInterface(object):
 
     # Fsck.
 
-    def get_fsck_work_items(self, settings):
+    def get_fsck_work_items(self):
         '''Returns fsck work items for checking this repository.
 
         This may be a generator or may return an iterable data
@@ -810,9 +810,6 @@ class RepositoryInterface(object):
         The returned work items are of type obnamlib.WorkItem. It may
         return further work items.
 
-        The settings argument is of type cliapp.Settings, and lets
-        the user affect what work gets done.
-
         '''
         raise NotImplementedError()
 
@@ -1208,7 +1205,7 @@ class RepositoryInterfaceTests(unittest.TestCase): # pragma: no cover
                 'fooclient', obnamlib.REPO_CLIENT_TEST_KEY)
             self.assertEqual(value, 'bar')
 
-    def test_setting_unallowed_client_key_fails(self):
+    def test_setting_disallowed_client_key_fails(self):
         self.setup_client()
         self.repo.lock_client('fooclient')
         self.assertRaises(
@@ -1223,7 +1220,7 @@ class RepositoryInterfaceTests(unittest.TestCase): # pragma: no cover
                 self.repo.set_client_key,
                 'fooclient', obnamlib.REPO_CLIENT_TEST_KEY, 'bar')
 
-    def test_committing_client_preserves_key_changs(self):
+    def test_committing_client_preserves_key_changes(self):
         if self.client_test_key_is_allowed():
             self.setup_client()
             self.repo.lock_client('fooclient')
@@ -1337,7 +1334,7 @@ class RepositoryInterfaceTests(unittest.TestCase): # pragma: no cover
                 gen_id, obnamlib.REPO_GENERATION_TEST_KEY)
             self.assertEqual(value, 'bar')
 
-    def test_setting_unallowed_generation_key_fails(self):
+    def test_setting_disallowed_generation_key_fails(self):
         if self.generation_test_key_is_allowed():
             gen_id = self.create_generation()
             self.assertRaises(
@@ -1353,7 +1350,7 @@ class RepositoryInterfaceTests(unittest.TestCase): # pragma: no cover
                 self.repo.set_generation_key,
                 gen_id, obnamlib.REPO_GENERATION_TEST_KEY, 'bar')
 
-    def test_committing_client_preserves_generation_key_changs(self):
+    def test_committing_client_preserves_generation_key_changes(self):
         if self.generation_test_key_is_allowed():
             gen_id = self.create_generation()
             self.repo.set_generation_key(
@@ -1589,7 +1586,7 @@ class RepositoryInterfaceTests(unittest.TestCase): # pragma: no cover
             gen_id, '/foo/bar', obnamlib.REPO_FILE_TEST_KEY)
         self.assertEqual(value, 'yoyo')
 
-    def test_setting_unallowed_file_key_fails(self):
+    def test_setting_disallowed_file_key_fails(self):
         gen_id = self.create_generation()
         self.repo.add_file(gen_id, '/foo/bar')
         self.assertRaises(
@@ -1875,7 +1872,7 @@ class RepositoryInterfaceTests(unittest.TestCase): # pragma: no cover
             set(self.repo.get_chunk_ids()),
             set([chunk_id_1, chunk_id_2]))
 
-    def test_have_not_got_chunk_indexes_lock_initally(self):
+    def test_have_not_got_chunk_indexes_lock_initially(self):
         self.setup_client()
         self.assertFalse(self.repo.got_chunk_indexes_lock())
 
diff --git a/obnamlib/structurederror.py b/obnamlib/structurederror.py
index 18c13e5a..16051743 100644
--- a/obnamlib/structurederror.py
+++ b/obnamlib/structurederror.py
@@ -100,8 +100,8 @@ class StructuredError(Exception):
         summer = hashlib.md5()
         summer.update(self.__class__.__name__)
         summer.update(self.__class__.__module__)
-        hash = summer.hexdigest()[:5]
-        return 'R{0}X'.format(hash.upper())
+        shorthash = summer.hexdigest()[:5]
+        return 'R{0}X'.format(shorthash.upper())
 
     def _format_msg(self, template):
         # In case template is a docstring, remove leading whitespace
diff --git a/obnamlib/structurederror_tests.py b/obnamlib/structurederror_tests.py
index b11909c0..9b24238b 100644
--- a/obnamlib/structurederror_tests.py
+++ b/obnamlib/structurederror_tests.py
@@ -62,11 +62,11 @@ class StructuredErrorTests(unittest.TestCase):
 
     def test_str_returns_first_line_only(self):
         first = FirstError()
-        self.assertNotIn('\n', str(first))
+        self.assertTrue('\n' not in str(first))
 
     def test_formatted_returns_full_message(self):
         first = FirstError()
-        self.assertIn('\n', first.formatted())
+        self.assertTrue('\n' in first.formatted())
 
     def test_formatted_message_does_not_end_in_whitespace(self):
         first = FirstError()
diff --git a/obnamlib/vfs.py b/obnamlib/vfs.py
index 3f99c045..7bf75f6c 100644
--- a/obnamlib/vfs.py
+++ b/obnamlib/vfs.py
@@ -15,7 +15,6 @@
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
 
-import errno
 import logging
 import os
 import stat
@@ -359,7 +358,7 @@ class VfsTests(object): # pragma: no cover
     * self.basepath to the path to the base of the filesystem
 
     basepath must be operable as a pathname using os.path tools. If
-    the VFS implemenation operates remotely and wants to operate on a
+    the VFS implementation operates remotely and wants to operate on a
     URL like 'http://domain/path' as the baseurl, then basepath must be
     just the path portion of the URL.
 
@@ -608,7 +607,7 @@ class VfsTests(object): # pragma: no cover
         self.assertEqual(self.fs.lstat('foo').st_atime_sec, 1)
         # not all filesystems support sub-second timestamps; those that
         # do not, return 0, so we have to accept either that or the correct
-        # value, but no other vlaues
+        # value, but no other values
         self.assert_(self.fs.lstat('foo').st_atime_nsec in [0, 2*1000])
 
         self.assertEqual(self.fs.lstat('foo').st_mtime_sec, 3)
diff --git a/obnamlib/vfs_local.py b/obnamlib/vfs_local.py
index 595795c4..c9b105e3 100644
--- a/obnamlib/vfs_local.py
+++ b/obnamlib/vfs_local.py
@@ -19,7 +19,6 @@ import errno
 import fcntl
 import grp
 import logging
-import math
 import os
 import pwd
 import tempfile
@@ -38,6 +37,11 @@ class MallocError(obnamlib.ObnamError):
     msg = 'malloc out of memory while calling {function}'
 
 
+class RootIsNotADirectory(obnamlib.ObnamError):
+
+    msg = '{baserurl} is not a directory, but a VFS root must be a directory'
+
+
 class LocalFSFile(file):
 
     def read(self, amount=-1):
@@ -95,7 +99,7 @@ class LocalFS(obnamlib.VirtualFileSystem):
         self.cwd = os.path.abspath(baseurl)
         if os.path.exists(self.cwd): # pragma: no cover
             if not os.path.isdir(self.cwd):
-                raise obnamlib.Error('%s is not a directory' % baseurl)
+                raise RootIsNotADirectory(baseurl=baseurl)
         if not self.isdir('.'):
             if create:
                 tracing.trace('creating %s', baseurl)
@@ -274,7 +278,7 @@ class LocalFS(obnamlib.VirtualFileSystem):
         return os.path.isdir(self.join(pathname))
 
     def mknod(self, pathname, mode):
-        tracing.trace('pathmame=%s', pathname)
+        tracing.trace('pathname=%s', pathname)
         tracing.trace('mode=%o', mode)
         os.mknod(self.join(pathname), mode)
 
@@ -402,7 +406,7 @@ class LocalFS(obnamlib.VirtualFileSystem):
                 ino = st.st_ino
             result.append((ino, name, st))
 
-        # We sort things in inode order, for speed when doing namei lookups
+        # We sort things in inode order, for speed when doing name lookups
         # when backing up.
         result.sort()
         return [(name, st) for ino, name, st in result]
diff --git a/obnamlib/vfs_local_tests.py b/obnamlib/vfs_local_tests.py
index 950675e4..eb497d2f 100644
--- a/obnamlib/vfs_local_tests.py
+++ b/obnamlib/vfs_local_tests.py
@@ -14,8 +14,6 @@
 # with this program; if not, write to the Free Software Foundation, Inc.,
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
-import platform
-import errno
 import os
 import shutil
 import tempfile
@@ -50,7 +48,7 @@ class LocalFSTests(obnamlib.VfsTests, unittest.TestCase):
     def test_get_groupname_returns_root_for_zero(self):
         # Some Unix systems have a wheel group instead of a root
         # group. We're fine with either.
-        self.assertIn(self.fs.get_groupname(0), ['root', 'wheel'])
+        self.assertTrue(self.fs.get_groupname(0) in ['root', 'wheel'])
 
 
 class XAttrTests(unittest.TestCase):
@@ -71,13 +69,13 @@ class XAttrTests(unittest.TestCase):
         # attribute with the command line tool.
 
         try:
-            exit, out, err = cliapp.runcmd_unchecked(
+            exitcode, out, err = cliapp.runcmd_unchecked(
                 ['setfattr', '-n', 'user.foo', 'bar', self.other])
         except OSError:
             # Either xattr aren't supported, or setfattr isn't
             # installed and we can't test.
             return False
-        return exit == 0
+        return exitcode == 0
 
     def test_empty_list(self):
         '''A new file has no extended attributes.'''
diff --git a/setup.py b/setup.py
index 9b541810..15f37f91 100755
--- a/setup.py
+++ b/setup.py
@@ -192,8 +192,8 @@ class Check(Command):
         os.remove('.coverage')
 
     def run_yarn(self):
-        for format in self.get_wanted_formats():
-            self.run_yarn_for_repo_format(format)
+        for repo_format in self.get_wanted_formats():
+            self.run_yarn_for_repo_format(repo_format)
 
     def get_wanted_formats(self):
         if 'REPOSITORY_FORMAT' in os.environ:
@@ -201,11 +201,11 @@ class Check(Command):
         else:
             return ['6', 'simple']
 
-    def run_yarn_for_repo_format(self, format):
-        print 'run yarn for repository format %s' % format
+    def run_yarn_for_repo_format(self, repo_format):
+        print 'run yarn for repository format %s' % repo_format
         runcmd(
             ['yarn', '-s', 'yarns/obnam.sh'] +
-            ['--env', 'REPOSITORY_FORMAT=' + format] +
+            ['--env', 'REPOSITORY_FORMAT=' + repo_format] +
             glob.glob('yarns/*.yarn'))
 
     def run_lock_test(self, num_clients, num_generations):