Executing command: ['bash', '--login', '-c', u'/usr/bin/rpmbuild -bb --target x86_64 --nodeps --define __spec_check_template exit 0;  /builddir/build/SPECS/python-ipaddress.spec']

Due to this in backend.py:

        if not check:
            # this is because EL5/6 does not know --nocheck
            # when EL5/6 targets are not supported, replace it with --nocheck
            check_opt += ["--define",  "__spec_check_template exit 0; "]

But then:

        if not util.USE_NSPAWN:
            command = ["bash", "--login", "-c"] + [' '.join(command)]

Which breaks because the argument has spaces.  Dunno about an easy fix, I'm just going to keep using nspawn.  But filing a bug as a FYI.