Removed PostgreSQL DatabaseWrapper._set_isolation_level().

        cursor.tzinfo_factory = utc_tzinfo_factory if settings.USE_TZ else None

        return cursor

    def _set_isolation_level(self, isolation_level):

        assert isolation_level in range(1, 5)     # Use set_autocommit for level = 0

        if self.psycopg2_version >= (2, 4, 2):

            self.connection.set_session(isolation_level=isolation_level)

        else:

            self.connection.set_isolation_level(isolation_level)

    def _set_autocommit(self, autocommit):

        with self.wrap_database_errors:

            if self.psycopg2_version >= (2, 4, 2):