Add back the helper function

tests/10apidoc/36room-levels.pl

@@ -0,0 +1,20 @@
+# Tests migrated to Complement as of https://github.com/matrix-org/complement/pull/545
+# However this helper function is used in other tests.
+
+push our @EXPORT, qw( matrix_change_room_power_levels );
+
+sub matrix_change_room_power_levels
+{
+   my ( $user, $room_id, $func ) = @_;
+   is_User( $user ) or croak "Expected a User; got $user";
+
+   matrix_get_room_state( $user, $room_id, type => "m.room.power_levels" )
+   ->then( sub {
+      my ( $levels ) = @_;
+      $func->( $levels );
+
+      matrix_put_room_state_synced( $user, $room_id, type => "m.room.power_levels",
+         content => $levels,
+      );
+   });
+}