Namespace packages, which have a name like "namespace.package" need to
be converted to paths in order to be found by flake8 - as the code
is in "namespace/package/".
In our setuptools integration command, we were attempting to avoid
checking each submodule in the packages list. This was done without
recognizing that two modules may start with the same prefix, e.g.,
- foo
- foo_bar
- foo_biz
In this case, we only ever checked ``foo``. By appending a '.' to the
end of each package name, we avoid this since we only care about
deduplicating submodules, e.g.,
- foo
- foo.sub
- foo.sub.sub
Closes#295