Since 9b6a1aafc3 was merged, all plugins
provided by neutron-lib are enabled automatically, as long as
neutron-lib is enabled.
This is a breaking change for any projects using neutron-lib,
especially ones outside of neutron's governance. While technically
we can ignore these checks, it'd be better to explicitly opt-in to
these checks to make sure new checks do not break pep8 check
immediately.
Closes-Bug: #2121609
Change-Id: I3a592f6170ab5215c1e0f2ebd7b9778141689932
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>