The python3-subunit RPM requires both Python 2 and Python 3.
Except in very special circumstances, there is no need for one package
to drag in both Python stacks. Usually, this is a packaging error: for
example, a stray "/usr/bin/python" shebang in a Python 3 package can
introduce a Python 2 dependency.
Please split your package, or remove the stray dependencies.
There is a section on shebangs in the Python RPM Porting Guide 
which covers this issue.
It's ok to do this in Rawhide only, however, it would be greatly
appreciated if you could push it to Fedora 24 as well.
If anything is unclear, or if you need any kind of assistance, you can
ask on IRC (#fedora-python on Freenode), or reply here. We'll be happy
to help investigating or fixing this issue!
subunit-1.2.0-7.fc24 has been submitted as an update to Fedora 24. https://bodhi.fedoraproject.org/updates/FEDORA-2016-6dace29fb4
subunit-1.2.0-7.fc24 has been pushed to the Fedora 24 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2016-6dace29fb4
Thank you for fixing the shebangs!
Could I ask if there is some reason why the `subunit-filters` RPM is using Python 2? If the executable works the same under Python 2 and Python 3, the packaging guidelines  advise to package the version for Python 3, as Python 2 is nearing the end of it's lifetime.
subunit-1.2.0-7.fc24 has been pushed to the Fedora 24 stable repository. If problems still persist, please make note of it in this bug report.
Reopening the bug as `subunit` is not fully Python 3 ready.
As per comment #3, `subunit-filters` RPM is Python 2 only, and to comply with the packaging guidelines it should either be switched to Python 3 or a Python 3 subpackage is to be provided.
Please let us know if you need any assistance or help with it.
The scripts in subunit-filters require pygtk2 to operate. As far as I know, pygtk2 is not available for python 3. Until that changes, or upstream switches to something other than pygtk2, subunit-filters must continue to depend on python 2.