Comment 3 for bug 518389

The disabled test checks (in an inconvenient way through timing) that .signature() is not called if the signature object (the object with a .signature() function) has already been placed in the memory cache. Since you've disabled placing signature objects in the memory cache, this fails. Since nobody has complained and ufl.Form.signature() caches the repr string itself anyway, this is probably ok. There are probably other places in instant with code designed to handle such object ids in the memory cache, but a cleanup here is a rather high risk operation and it probably doesn't hurt anyone.