Hook failues due DB InsufficientPrivilege

I deployed the charm on bionic, related to postgres using "db" relation and it failed with:

2018-05-31 11:31:19 INFO juju-log db:39: Ruby error: ['rake aborted!', 'StandardError: An error has occurred, this and all later migrations canceled:', 'PG::InsufficientPrivilege: ERROR: permission denied to create extension "hstore"', 'HINT: Must be superuser to create this extension.', ': CREATE EXTENSION IF NOT EXISTS hstore', "/var/lib/gems/2.4.0/gems/rack-mini-profiler-1.0.0/lib/patches/db/pg.rb:92:in `async_exec'", "/var/lib/gems/2.4.0/gems/rack-mini-profiler-1.0.0/lib/patches/db/pg.rb:92:in `async_exec'", "/var/lib/gems/2.4.0/gems/activerecord-5.1.4/lib/

Full error: https://pastebin.canonical.com/p/XX33rqxBR3/

I switched to db-admin relation and that worked around it.