After upgrading from Ubuntu 18.04 to 20.04 "sudo openproject configure" failed because the database version was insufficient. I upgraded to PG 12, following the instructions here https://gorails.com/guides/upgrading-postgresql-version-on-ubuntu-server. After that I retried to run the configuration script but got an error.

-- execute("CREATE EXTENSION IF NOT EXISTS btree_gist; ALTER TABLE journals ADD CONSTRAINT non_overlapping_journals_validity_periods EXCLUDE USING gist (journable_id WITH =, journable_type WITH =, validity_period WITH &&) DEFERRABLE")
rake aborted!
StandardError: An error has occurred, this and all later migrations canceled:

PG::InsufficientPrivilege: ERROR:  permission denied to create extension "btree_gist"
HINT:  Must be superuser to create this extension.

Configuration script was called as root. Database user for openproject is not privileged though.

EDIT:

This is how the access privileges of the database look like

# \l
                                     List of databases
   Name     |    Owner    | Encoding |   Collate   |    Ctype    |    Access privileges     
-------------+-------------+----------+-------------+-------------+--------------------------
openproject | postgres    | UTF8     | en_GB.UTF-8 | en_GB.UTF-8 | postgres=CTc/postgres   +
            |             |          |             |             | =Tc/postgres            +
            |             |          |             |             | openproject=CTc/postgres

/EDIT