putting it in requirements means it's installed for anything that
installs diskimage-builder. Not just for tests, but in actual prod
installations. Because of the way flake8 plugins work, this means
then that hacking is injected into all flake8 invocations in that
This is currently causing issues in nodepool where we do not
actually use hacking but it's still spewing spurious messages to
the screen because it is incorrect finding our apache header to be
Just depend on flake8, since that's what dib-lint depends on.