Missing parser tests

[tristanlatr]

This adds some tests from the pydoctor test suite: https://github.com/twisted/pydoctor/blob/master/pydoctor/test/test_configparser.py

[tristanlatr]

There is probably some kind of regression! All tests should be passing

[kingbuzzman]

Heh, theres some overlap here https://github.com/bw2/ConfigArgParse/pull/317

[tristanlatr]

Having more or less duplicated tests isn’t too bad. The real question is why it isn’t passing :/ Since it is passing as-is in pydoctor’s test cases… some troubleshooting is required