> But... there is no os.unsetenv on Windows!
Correct, even unsetenv() doesn't exist on Windows: putenv() can be used to unset a variable using an empty value. And it's exactly what Python does.
It is confusing because posix_unsetenv() is not build on Windows, but it contains code specific for Windows.
While testing del os.environ[key], I found another bug: del os.environ['x'*50000] does crash Python on Windows.
Attached patch (for Python 3.3) does:
- Remove the Windows specific code from posix_unsetenv()
- Check if unsetenv() failed on UNIX
- Check environment variable length on Windows
The Windows bug does affect Python 2.7 too. "Check if unsetenv() failed on UNIX" change may be skipped on Python 2.7 and 3.2.