The change done for issue9291 in Python 2.7.7 caused the mimetypes.types_map dict to change to contain a mixture of str and unicode objects, rather than just str, as it always had before.

This causes twisted.web to crash when serving static files on Windows. See https://twistedmatrix.com/trac/ticket/7461 for the bug report against Twisted.

Issue also exists in Pyramid (any wsgi server/framework) See https://github.com/Pylons/pyramid/issues/1360 for Pyramid bug.

If there is a regression to be fixed, there needs to be a patch with a test.  Anyone?

Reverting the incorrect commit which caused the regression would be a good start.

If I understand correct that patch was itself attempting to fix a regression ;)

Only if you have something better to put in its place! That commit was
fixing an existing problem; perhaps not your problem, but someone's. To
revert it would simply move the pain around.

I hope to be able to work on this fairly soon. If anyone else wants to
propose an approach to take this forward, they're welcome to do so.

> That commit was fixing an existing problem; perhaps not your problem, but someone's. To revert it would simply move the pain around.

Doesn't the very same logic apply to the original commit?

> I hope to be able to work on this fairly soon.

Thanks.  Much appreciated.

Did anyone here managed to reproduce the issue?
I tired but I have failed to.
I'm still trying though. 

Anyway I'd start from investigating why a function EnumKey returns Unicode object while according to documentation it should return string.

I can reproduce the issue with the attached script. The problem is not that EnumKey returns a Unicode string (which it never does), but that QueryValueEx returns a Unicode string. See http://hg.python.org/cpython/rev/18cfc2a42772 for the actual change in question.

Thanks, Martin. I didn't read the final with enough care. I think the second part of changes (the ones that are around QueryValueEx) should be rolled back. I believe the code was correct at that part.
Tim, what do you think?

Vladimir, if you could provide a patch implementing your proposed rollback, that would be appreciated.

Finally I got environment and some time.
Attaching patch.

New changeset 1aafbdfba25a by Benjamin Peterson in branch '2.7':
don't allow unicode into type_map on Windows (closes #21652)
http://hg.python.org/cpython/rev/1aafbdfba25a

Thanks Vladimir; I really appreciate your work on these issues.