sql: do not attempt to create the plpgsql lang if already exists
This is needed in case the pg user is not super user (but language already exists.)
Migrated from D2776 (view on Phabricator)
Staging instance, all changes can be removed at any time
This is needed in case the pg user is not super user (but language already exists.)
Migrated from D2776 (view on Phabricator)