Running ‘dispatch database upgrade’ seems stuck.

Most likely, the upgrade is stuck because an existing query on the database is holding onto a lock that the migration needs.

To resolve, login to your lemur database and run:

SELECT * FROM pg_locks l INNER JOIN pg_stat_activity s ON (l.pid = s.pid) WHERE waiting AND NOT granted;

This will give you a list of queries that are currently waiting to be executed. From there attempt to idenity the PID of the query blocking the migration. Once found execute:

select pg_terminate_backend(<blocking-pid>);

See http://stackoverflow.com/questions/22896496/alembic-migration-stuck-with-postgresql for more.