Rails + Postgres drop error: database is being accessed by other users

I have a rails application running over Postgres.

I have two servers: one for testing and the other for production.

Very often I need to clone the production DB on the test server.

The command I'm runnig via Vlad is:

rake RAILS_ENV='test_server' db:drop db:create

The problem I'm having is that I receive the following error:

ActiveRecord::StatementInvalid: PGError: ERROR: database <database_name> is being accessed by other users DROP DATABASE IF EXISTS <database_name>

This happens if someone has accessed the application via web recently (postgres keeps a "session" opened)

Is there any way that I can terminate the sessions on the postgres DB?

Thank you.

Edit

I can delete the database using phppgadmin's interface but not with the rake task.

How can I replicate phppgadmin's drop with a rake task?