I am sure this is intended behavior but it seems odd (and inconvenient) to me.
create database tim_test_copy template tim_test
ERROR: source database "tim_test" is being accessed by other users
DETAIL: There are 1 other session(s) using the database.
I would presume only reads are required from tim_test but apparently I
have to resort to pg_dump and pg_restore to clone an active database.