AdminChooser needs to be replaced with BaseChooser

[Scotchester]

When using the latest release with Wagtail 4, this warning is thrown:

usr/local/lib/python3.8/dist-packages/wagtail/admin/widgets/chooser.py:37: 
RemovedInWagtail50Warning: wagtail.admin.widgets.chooser.AdminChooser is deprecated.
Custom chooser subclasses should inherit from wagtail.admin.widgets.chooser.BaseChooser instead.

AdminChooser was replaced by BaseChooser in Wagtail 4.0, so wagtailmedia should be updated here:

wagtailmedia/src/wagtailmedia/widgets.py

Line 26 in 08e06e6

class AdminMediaChooser(AdminChooser):

[zerolab]

I believe there's more than that involved in making this happen, but that is the correct place.
PR(s) welcome

[nickmoreton]

I noticed that a failing test for wagtail-webstories is because of this import.

wagtailmedia/src/wagtailmedia/widgets.py

Line 10 in cafdf36

from wagtail.admin.widgets import AdminChooser

I'll have a better look around and put in a PR for it.

[nickmoreton]

I'll have a better look around and put in a PR for it.

I see what you mean @zerolab there's more to it. I don't have time for this at the moment 😞

[zerolab]

Fixed in #199