Submitted a backport for upstream queens: https://review.openstack.org/568555
I requested Release oslo.utils 3.35.1 for Queens: https://review.openstack.org/#/c/572373/
I cannot rebase oslo.utils to 3.35.1 because this issue is not marked as a blocker issue. Since the issue only impacts log in DEBUG mode, I don't think that it deserves to block the release. It can wait for a z-stream release. If you disagree, please mark the issue as a blocker, so I can do the rebase :-)
While the Oslo part is done, keystoneauth needs to be modified to use mask_password(): see https://bugzilla.redhat.com/show_bug.cgi?id=1578347#c11 I changed the component of this issue to openstack-keystone.
Since that bug requires a fix in both python-oslo-utils and openstack-keystone, I have just clone it [1] to track the python-oslo-utils fix in a dedicated bz. [1] https://bugzilla.redhat.com/show_bug.cgi?id=1612890