Today I was trying to compile a module using an extension in C and
noticed there are differences between compiling it on Python 2.5 and 2.6.
I was trying to compile psutil (svn checkout
http://psutil.googlecode.com/svn/trunk/ psutil) but I think that the
problem may occur with any other package using C extensions.

Python 2.5:

D:\pyftpdlib\svn\psutil\trunk>C:\python25\python.exe setup.py install
running install
running build
running build_ext
error: Python was built with Visual Studio 2003;
extensions must be built with a compiler than can generate compatible
binaries.
Visual Studio 2003 was not found on this system. If you have Cygwin
installed,
you can try compiling with MingW32, by passing "-c mingw32" to setup.py.



Python 2.6:

D:\pyftpdlib\svn\psutil\trunk>C:\python26\python.exe setup.py install
running install
running build
running build_ext
building 'psutil/_psutil_mswindows' extension
error: None

What is the specific error you are reporting?

Currently I haven't any C compiler installed on my system so I expect
distutils to report that every time I try to compile a C module extension.
Python 2.5 did that while Python 2.6 does not.

The problem has two causes:
- IOError is raised when no compiler is found. DistutilsPlatformError
should be used instead, this was fixed by #4702.

- the distutils.util.grok_environment_error function transforms a
IOError("Unable to find vcvarsall.bat") into "error: None".

This function should not be used IMO. Its docstring claims that it
"Handles Python 1.5.1 and 1.5.2 styles", but str() does a better job...

Patch attached.

Tarek: This patch seems reasonable to me, is this something that can be applied?

I guess i can be applied on distutils, and backported in distutils2. I'll do it in the coming days.

Notice that I am now applying only bug fixes and regression fixes now for distutils.

I will commit this if Tarek does not do it shortly.

In distutils2, I’ll remove grok_environment_error wholly, since it exists for 1.5 compat only.

Giampaolo, can you test Amaury’s patch?  I’d prefer some testing before committing.

I don't have the same setup I had at the time when I submitted the first message so maybe something has changed in meantime.
Below is what I get on Windows 2000 SP-3, no VS installed, python 2.7, before and after the patch.

C:\Documents and Settings\foo\Desktop\psutil>setup.py build
running build
running build_py
copying psutil\compat.py -> build\lib.win32-2.7\psutil
copying psutil\error.py -> build\lib.win32-2.7\psutil
copying psutil\_psbsd.py -> build\lib.win32-2.7\psutil
copying psutil\_pslinux.py -> build\lib.win32-2.7\psutil
copying psutil\_psmswindows.py -> build\lib.win32-2.7\psutil
copying psutil\_psosx.py -> build\lib.win32-2.7\psutil
copying psutil\_psposix.py -> build\lib.win32-2.7\psutil
copying psutil\__init__.py -> build\lib.win32-2.7\psutil
running build_ext
building '_psutil_mswindows' extension
error: Unable to find vcvarsall.bat


Although the message is improved ("Unable to find vcvarsall.bat" vs "None") it seems the patch had no effect.

Any chance of getting this patch applied? It clearly makes the error message more useful, and we've run into another case where grok_environment_error gives the wrong result: when symlinking fails because the target exists, it now says "File exists: <source>", because e.filename is the source and e.filename2 the target.

It's also rather embarassing that a function in Python 3.4 still says "Handles Python 1.5.1 and 1.5.2 styles..." in the docstring.

I want to make time for Python bugs again, so I’ll try and finish this bug soon.

See also msg200785 for a report from setuptools with an easy to reuse test case.

New changeset a865f6fb82b4 by Éric Araujo in branch '2.7':
Avoid “error: None” messages from distutils (#4931).
http://hg.python.org/cpython/rev/a865f6fb82b4

New changeset 0f1237b61f58 by Éric Araujo in branch '2.7':
Restore missing part of error message (#4931)
http://hg.python.org/cpython/rev/0f1237b61f58

New changeset 504eb00998f2 by Éric Araujo in branch '3.3':
Avoid “error: None” messages from distutils (#4931).
http://hg.python.org/cpython/rev/504eb00998f2

New changeset c7bd0f953687 by Éric Araujo in branch 'default':
Merge 3.3 (#4931)
http://hg.python.org/cpython/rev/c7bd0f953687

Happy to close this as fixed.