twisted.python.rebuild.rebuild dies if something's __hash__ raises an exception other than TypeError

[z3p]

This came up in #3391, where PyASN1 causes this to fail test_rebuild.

[z3p]

(In [26824]) Branching to 'rebuild-hash-fail-3817'

[z3p]

Did I say 'enhancement'? I meant 'defect'.

[z3p]

Ready for review.

[exarkun]

1. twisted/test/test_rebuild.py
   1. name all new test methods test_foo instead of testFoo
   2. use two blank lines between new or modified methods and the method preceding or following; use three between a method and the start of the next class
   3. It might be nice to avoid adding an unhashable attribute to test_rebuild permanently (in case some other tool can't handle this case). The test could set the attribute when it starts and use addCleanup to make sure it is deleted when the test is over. (this is an optional review comment)

Please merge when all points are addressed.

[z3p]

(In [26910]) Don't fail the rebuild if an object cannot be hashed.

Author: z3p Reviewer: exarkun Fixes #3817

Previously, only a TypeError was ignored for objects during a module rebuild. Some objects raise other errors (notably the PyASN1 module) and caused the test_rebuild tests to fail.