Jenkins fails because flake8 reports over-indented line here.

Same here.

Looks good to me. Tests are passing locally for me.

I've added a commit fixing the whitespace. Sorry for that!

Looks good to me.

In addition, I have an idea about passing argument to underlying command. That is, instead of adding arguments to rpkg or fedpkg and passing to underlying command, how about we add one general argument used to pass any potential required extra command line options? To be clear, here is an example,

fedpkg mockbuild -r fedora-25-x86_64 --addopts "--shell --with"

Maybe --addopts could be --extra_opts or something else that can reflect the meaning as much as possible.

That seems unnecessary to me: I don't view rpkg as a generic front-end to mock, and I'm quite happy doing fedpkg srpm and mock manually for complex cases. Note that in these complex cases, I'll usually want to run mock --shell or mock --install without building a package. I don't think combining that with fedpkg mockbuild would make things straightforward.

My use case for --with is that Python's full optimized build and test suite take half an hour, so my usual local builds need --without optimizations.

I don't think passing arbitrary options is particularly useful. Let's not do it unless someone comes with a use case for it.

Is there anything else I can do to help this get merged?