Add support for the upcoming Django 3.2

[matthiask]

The CountryField uses super() in a few methods to skip CharField's methods and call methods of the CharField's superclass directly. Django 3.2 adds support for db_collation to CharField, but the CountryField doesn't need this. Since CountryField.__init__ does not call CharField.__init__, CountryField.deconstruct shouldn't call CharField.deconstruct either.

Also, Django 3.1 and django-rest-framework 3.10.x are not compatible because django-rest-framework imports the FieldDoesNotExist exception from location where it isn't available anymore in Django 3.1. Therefore, this pull request also removes this combination from the CI matrix.

Replaces #328

[codecov-io]

Codecov Report

Merging #329 (b7f18ba) into master (96c188a) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #329   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           27        27           
  Lines         1385      1385           
=========================================
  Hits          1385      1385           

Impacted Files	Coverage Δ
django_countries/fields.py	100.00% <100.00%> (ø)

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[matthiask]

I have added Django 3.2a1 to the CI matrix. All tests fail without the super() change. With the change all tests pass.

[matthiask]

Hmm, all tests do NOT pass, but the reason seems to be an incompatibility of Django and django-rest-framework.

[matthiask]

Tests are passing now; I updated the description of this pull request to better reflect what it is all about.

[matthiask]

I found a good workaround for the time being.

Add the following lines e.g. to your settings.py file:

if True:
    import django_countries.fields  # noqa

    django_countries.fields.CountryField.db_collation = None

[SmileyChris]

Thanks Matthias, I'll get a version pushed out tomorrow

[domdinicola]

is this already fixing the "db_collation" error for CountryField?

[matthiask]

@domdinicola Yes.

[Mogost]

@SmileyChris Could you release a new version please?

[SmileyChris]

Released as v7.1