Handle queryset implementations without lhs/rhs attribute (#204)
Handle queryset implementations without lhs/rhs attribute (#204)

The `ExtraJoinRestriction` class used by django-taggit lacks the
attributes "rhs" and "lhs".
Thus projects cannot use django-taggit together with cachalot.

Closes: #121
BertrandBordage/django-cachalot,BertrandBordage/django-cachalot