Flake8 3.0 was stopping once it found the current directory but the
historical behaviour (that we didn't intend to break) searched past
that (towards root) until it found one of the project/local config
file names that could be read.
Closes#181
If somebody explicitly has a `.flake8` file, presumably they intend to
put flake8 configuration in it, so prefer it to the generic `setup.cfg`
and `tox.ini` from pycodestyle.
This relies on two things:
1. Properly configuring flake8-import-order to use that style
2. Properly configuring flake8-import-order to know that flake8 is our
application name.
ConfigFileFinder should absolutely handle broken/invalid config files
by refusing to try to parse them. Here we catch the ParsingError,
log the exception, and then return normally. The RawConfigParser
instance is perfectly valid still and will behave as if nothing had
been read and we just need to indicate that we didn't find any files
worthy of reading.
Related to: https://github.com/PyCQA/pycodestyle/issues/506
Python 2.7's ConfigParser module does not allow for the behaviour we
have documented for config files in Flake8 3.0. To compensate for that,
we add a dependency on the configparser backport on PyPI for Python 2.7
