The CREATE SCHEMA reference page says "Only superusers can create
schemas owned by users other than themselves". ISTM this is incorrect,
or at least not the whole truth, because the test that is actually in
the code is check_is_member_of_role(), that is whether the current user
is allowed to SET ROLE to the target.
In the SET ROLE reference page we say "The specified role_name must be a
role that the current session user is a member of. (If the session user
is a superuser, any role can be selected.)" Is that good wording to use
in CREATE SCHEMA too, or would somebody like to wordsmith it?
regards, tom lane