refactor(templates/python): drop magic cookie for environment vars

We previously changed the Python template to set TMPDIR to the
per-scenario directory. Part of that was using a "magic cookie" value
to indicate which environment variables to set to the scenario
directory. The cookie is unnecessary: we can just set the environment
variables at the start of the scenario. This commit does that.

2 files changed, 12 insertions, 27 deletions

diff --git a/templates/python/main.py b/templates/python/main.py
index 7f55765..05e1715 100644
--- a/templates/python/main.py
+++ b/templates/python/main.py
@@ -28,29 +28,6 @@ def parse_command_line():
     return p.parse_args()
 
 
-# Any environment variables set to this value will be set to the data directory
-# for each scenario, when the scenario starts.
-_DATADIR_COOKIE = "set-this-to-datadir-for-each-scenario"
-
-
-def setup_minimal_environment():
-    minimal = {
-        "PATH": "/bin:/usr/bin",
-        "SHELL": "/bin/sh",
-        "HOME": _DATADIR_COOKIE,
-        "TMPDIR": _DATADIR_COOKIE,
-    }
-
-    os.environ.clear()
-    os.environ.update(minimal)
-
-
-def set_environment_variables_to(scendir):
-    for key in os.environ:
-        if os.environ[key] == _DATADIR_COOKIE:
-            os.environ[key] = scendir
-
-
 def setup_logging(args):
     if args.log:
         fmt = "%(asctime)s %(levelname)s %(message)s"
@@ -78,7 +55,6 @@ def save_directory(dirname, tarname):
 
 def main(scenarios):
     args = parse_command_line()
-    setup_minimal_environment()
     setup_logging(args)
     logging.info("Test program starts")
 
diff --git a/templates/python/scenarios.py b/templates/python/scenarios.py
index 6dbc1a8..eb5302e 100644
--- a/templates/python/scenarios.py
+++ b/templates/python/scenarios.py
@@ -60,14 +60,12 @@ class Scenario:
         self._steps.append(step)
 
     def run(self, datadir):
-        set_environment_variables_to = globals()["set_environment_variables_to"]
-
         print("scenario: {}".format(self._title))
         logging.info("Scenario: {}".format(self._title))
 
         scendir = tempfile.mkdtemp(dir=datadir)
         os.chdir(scendir)
-        set_environment_variables_to(scendir)
+        self._set_environment_variables_to(scendir)
 
         done = []
         ctx = self._ctx
@@ -82,3 +80,14 @@ class Scenario:
             raise
         for step in reversed(done):
             step.cleanup(ctx)
+
+    def _set_environment_variables_to(self, scendir):
+        minimal = {
+            "PATH": "/bin:/usr/bin",
+            "SHELL": "/bin/sh",
+            "HOME": scendir,
+            "TMPDIR": scendir,
+        }
+
+        os.environ.clear()
+        os.environ.update(minimal)