'in' operator support not implemented for twisted.python.modules.PythonPath

[itamar]

>>> from twisted.python.modules import theSystemPath
>>> theSystemPath["os"]
PythonModule<'os'>
>>> "os" in theSystemPath
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "twisted/python/modules.py", line 699, in __getitem__
    if '.' in modname:
TypeError: argument of type 'int' is not iterable

[exarkun]

(In [36617]) Branching to 'modules-contains-6198'

[exarkun]

(In [36618]) apply pythonpath-contains-6198.patch

refs #6198

[exarkun]

Thanks! This looks pretty good. I have a few comments though:

1. A test should cover one case. Since unittest uses exceptions to signal failures, any assertions that follow a failing assertion won't run. This means failures may exist that won't get reported, if they happen to be checked after another failure. Testing each case in a dedicated test method provides better reporting by showing all failures instead of just some (which means you don't have to run the test suite as many times, and you can be more confident that once you fix some failures, all tests will be passing).
2. Use L{} to refer to functions, classes, or modules in a docstring.
3. Test method docstrings should not use the word should.
4. This new feature should be described by a news fragment file.

These are pretty straightforward changes. I'll make them and, if buildbot is green, merge. Thanks.

[exarkun]

(In [36619]) address review comments

refs #6198

[exarkun]

 Build results

[exarkun]

(In [36622]) minor doc improvement

refs #6198

[exarkun]

(In [36623]) Merge modules-contains-6198

Author: ephess Reviewer: exarkun Fixes: #6198

Implement the in operator for right-hand values of type twisted.python.modules.PythonPath.