Update InheritanceIterable to inherit from ModelIterable instead of BaseIterable

[hanleyhansen]

Problem

This PR addresses issue #277

Solution

The solution required updating InheritanceIterable to inherit from ModelIterable instead of BaseIterable to avoid the exception thrown in Django 1.11's query.py:

if queryset is not None and not issubclass(queryset._iterable_class, ModelIterable):
    raise ValueError('Prefetch querysets cannot use values().')

The test exposes that this was broken in Django 1.10 also, hence the skipIf. However, in Django 1.10 the if requires a ModelIterable not just a subclass of it which is a lot more restrictive:

if queryset is not None and queryset._iterable_class is not ModelIterable:
    raise ValueError('Prefetch querysets cannot use values().')

Commandments

• Write PEP8 compliant code.
• Cover it with tests.
• Update CHANGES.rst file to describe the changes, and quote according issue with GH-<issue_number>.
• Pay attention to backward compatibility, or if it breaks it, explain why.

[nherzing]

Any timeline for getting this merged?

[wmorrell]

It's been four months since the PR submitted, could this please get merged in? As of now, django-model-utils will not work with Django 1.11+ if a Prefetch is used.

[and3rson]

Any updates? This is absolutely critical.

[eranrund]

Any news? This is making our lives hard :(

[geoolekom]

Please, merge it, prefetching is essential for us.

[jezdez]

Hey folks, a Jazzband roadie here.

Did you know you can merge this yourself? Simply join Jazzband and you'll able to help out directly with maintenance of this package.

Check out the Jazzband FAQ for more info what Jazzband is and how it works.

[hanleyhansen]

Thanks @jezdez. Just joined!

[hanleyhansen]

@jezdez do we also manage pypi releases?

[jezdez]

@hanleyhansen Releases happen semi-automatic as documented on the Releases site, basically @carljm will need to approve a release manually once a Git tag has been cut which triggers the upload to the release stage. Make sure to update the version number in the various places (e.g. model_utils/__init__.py) before you create the tag and document the changes according to the project's practices.