Django 1.10 functional middleware compatibility

[ryankask]

debug_toolbar.apps.is_middlware_class() is used in a check for middleware ordering issues.

It assumes that all middleware in MIDDLEWARE are classes and doesn't account for Django 1.10's functional middleware.

If a functional middleware factory is present, it fails when it hits issubclass() since the first argument isn't a class.

I will try to submit a patch this weekend because I need to clone the project and get the test suite running but a simple solution would be tweak it:

def is_middleware_class(middleware_class, middleware_path):
    try:
        middleware_cls = import_string(middleware_path)
    except ImportError:
        return
    try:
        return issubclass(middleware_cls, middleware_class)
    except TypeError:
        return False

Perhaps there is a more elegant check using the types module but I would need to read about Py2/3 compatibility.

[ryankask]

Submitted PR #879 using a more explicit check.

[Benoss]

I think this is already covered in this
#853
The pull request is already merged but no releases since

[matthiask]

Thanks!

@Benoss The check for middleware ordering is still there, and should be fixed if it fails now.

I'll test it in a project of mine and merge if I don't hit any additional problems.

[matthiask]

That's the same issue as #874 by the way. Closing this issue as duplicate.

[jhancia]

Any chance we could have a new PyPi release to incorporate these changes? Thank you so much!