EntityFilter issue with M2M fields

[hsmett]

When creating an EntityFilter for with two conditions targeting the same M2M field, the resulting listview items are incorrect.
For exemple, given

    Class Stuff(CremeEntity):
        things = models.ManyToManyField(Thing ...)

The stuff resulting from a filter with conditions (things = a_thing) & (things != another_thing) would be wrong.

[genglert]

There's a workaround: move one of the conditions in a sub-filter.
Edit: a condition '!=' + a sub-filter with the condition '=' (order is important).