Description of problem:
Accidentally introduced when via #1570941 and its associated backports.
$ tox -e pep8
[..]
./nova/conf/libvirt.py:27:1: F811 redefinition of unused 'types' from line 25
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.
https://access.redhat.com/errata/RHSA-2018:2332