Because the setup.cfg included in U/S neutron tarballs  include tabs instead of spaces, and patches expect it to have spaces, rpmbuild can't apply patches that modify this file.
Although there's an RFE  to do this, in the meantime we can submit a double patch on top of the latest tagged commit:
1. Patch that uses the setup.cfg from the tarball (with tabs) - DROP-IN-RPM
2. Patch that uses the setup.cfg from git (with spaces and comments)
After this, all git patches that modify setup.cfg should apply and the RPM package should build normally.
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.