Exception: 'NameError: name 'reload' is not defined' when using mod_python with Python 3.x

[john.de.rooij@…]

When Trac 1.5.3 is used in combination with mod_python on an Apache2 server, together in combination with Python 3.9, a 'NameError: name 'reload' is not defined' exception is raised.

The reload function which was a builtin function in Python 2.x has moved to the imp module or the importlib module depending on the actually used Python 3.x version. Because this problem in present in the modpython_frontend.py it will only be present when mod_python is used. A 'tracd' installation will not show this problem.

This is also the only reload call that is present in the complete trac sourcecode.

The relevant python backtrace is:

PythonHandler trac.web.modpython_frontend: NameError: name 'reload' is not defined
PythonHandler trac.web.modpython_frontend: Traceback (most recent call last):
PythonHandler trac.web.modpython_frontend:   File "/usr/lib/python3/dist-packages/mod_python/apache.py", line 398, in HandlerDispatch\n    result = obj(req)
PythonHandler trac.web.modpython_frontend:   File "/usr/local/lib/python3.9/dist-packages/trac/web/modpython_frontend.py", line 146, in handler\n    reload(sys.modules['trac.web'])

A diff patch to resolve this problem is also attached.

[john.de.rooij@…]

Patch: Use reload from the correct module depending on the running Python version

[Jun Omae]

Thanks for the reporting. I missed that ​reload() has been removed in Python 3.0.

$ pyflakes trac/web/modpython_frontend.py
trac/web/modpython_frontend.py:146: undefined name 'reload'

We could use simply importlib.reload(), because Trac 1.5.3 requires Python 3.5+.

trac/web/modpython_frontend.py

@@ -16 +16 @@
 # Author: Christopher Lenz <cmlenz@gmx.de>
 #         Matthew Good <trac@matt-good.net>
 
+import importlib
 import os
 import pkg_resources
 import sys
@@ -143 +144 @@
                 egg_cache = req.subprocess_env.get('PYTHON_EGG_CACHE')
             if egg_cache:
                 pkg_resources.set_extraction_path(egg_cache)
-            reload(sys.modules['trac.web'])
+            importlib.reload(sys.modules['trac.web'])
     pkg_resources.require('Trac==%s' % VERSION)
     gateway = ModPythonGateway(req, req.get_options())
     from trac.web.main import dispatch_request

[john.de.rooij@…]

Ok. I just wanted to provide a generic solution that works for every used Python version.

Because Python ≥ 3.5 is a requirement for Trac 1.5, it is indeed also ok, and simpler to use the changes you suggested.

Can you apply your diff on trunk?

[Jun Omae]

Committed in [17571].