Use our patched version of docker-py with build credentials patched in. Fix the hostname in the build credentials block to be variable.

data/model/legacy.py

@@ -1471,7 +1471,7 @@ def get_pull_credentials(trigger):
   return {
     'username': trigger.pull_user.username,
     'password': login_info.service_ident,
-    'registry': 'quay.io' # TODO: Is there a better way to do this?
+    'registry': app.config['URL_HOST'],
   }
 
 def create_webhook(repo, params_obj):