AttributeError: 'NoneType' object has no attribute 'startswith' when running under pytest

[dstufft]

Apparently pytest puts a module into sys.modules with a None key, this causes this code:

freezegun/freezegun/api.py

Line 199 in aa72636

if mod_name.startswith(tuple(self.ignore)):

to bomb out because None.startswith() doesn't work.

Probably this should have a check above it looking for if mod_name is None: continue as well.