Description of problem: python-netaddr FTBFS on Python 3.7

It raises StopIteration from generator. That is now a runtime error. See 


Version-Release number of selected component (if applicable): python-netaddr-0.7.19-10.fc29


How reproducible: in koji


Steps to Reproduce:
1. fedpkg build --target=f29-python

Especially please don't just fedpkg build without target.

Actual results:
E           RuntimeError: generator raised StopIteration

=> package FTBFS

Expected results:
package builds

Additional info:
https://docs.python.org/3.7/whatsnew/3.7.html#changes-in-python-behavior
https://www.python.org/dev/peps/pep-0479/

Similar bugs/fixes:
https://bugzilla.redhat.com/show_bug.cgi?id=1583818
https://bitbucket.org/ianb/paste/pull-requests/41/python-37-support/diff
https://github.com/erikrose/more-itertools/commit/e38574428c952b143fc4e0e42cb99b242c7b7977