st2ctl says it is ignoring content in a directory, but then warns of bad content in that directory

While running through the README for the sensu pack, I encountered the following WARNING message that confused me:

FYI, packs_base_path = /opt/stackstorm/packs.dev

(sensu) root@2e1d15fd5d07:/etc/sensu/handlers# st2ctl reload --register-all
Registering content...[flags = --config-file /etc/st2/st2.conf --register-all]
2017-06-29 05:15:57,631 INFO [-] Connecting to database "st2" @ "mongo:27017" as user "None".
2017-06-29 05:15:57,765 INFO [-] =========================================================
2017-06-29 05:15:57,766 INFO [-] ############## Registering triggers #####################
2017-06-29 05:15:57,766 INFO [-] =========================================================
2017-06-29 05:16:07,033 WARNING [-] Pack "sensu" already found in "/opt/stackstorm/packs", ignoring content from "/opt/stackstorm/packs.dev"
2017-06-29 05:16:07,080 WARNING [-] Failed to register sensors: Failed to register trigger "/opt/stackstorm/packs.dev/stackstorm-sensu/triggers/event_handler.yaml" from pack "stackstorm-sensu": Model is in pack "stackstorm-sensu" but field "pack" is different: sensu
...
ValueError: Failed to register trigger "/opt/stackstorm/packs.dev/stackstorm-sensu/triggers/event_handler.yaml" from pack "stackstorm-sensu": Model is in pack "stackstorm-sensu" but field "pack" is different: sensu

I'll dig into this when I get a chance, unless someone has a ready explanation for this behavior.

Start with the sensu pack README steps and the st2ctl reload --register-all entry point, then trace how the duplicate pack paths are handled during registration. Done means the command's ignore behavior and subsequent registration warning are consistent and the reported scenario is covered by an appropriate test or documented explanation.