Comment 3 for bug 1696396

To elaborate a little about the issue, this was because we changed devstack heat to use uwsgi
by default from pike onwards in https://review.openstack.org/#/c/462216

That change was reverted by https://review.openstack.org/#/c/471730/

However, we would push that change again with https://review.openstack.org/#/c/478345/

The above issue could have been resolved by:

1. Using heatclient >= 1.10.0
2. Adding 'AlllowEncodedSlashes On' in apache config for compatibility with old heatclients.

Note: This would only be case with fresh devstack that uses apache+uwsgi by default.