Remove hard coded dependency on stats from the files app

[kimakan]

Closes #248

[coveralls]

Pull Request Test Coverage Report for Build 11233210493

Details

• 1 of 4 (25.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.02%) to 63.968%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
daiquiri/files/utils.py	1	4	25.0%
<!--	Total:	1	4	25.0%	-->

Totals
Change from base Build 10420115417:	-0.02%
Covered Lines:	4820
Relevant Lines:	7535

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💛 - Coveralls

[jochenklar]

Hi @kimakan , while this should work, the django way to do this would be:

from django.apps import apps

if apps.is_installed('daiquiri.stats'):
    from daiquiri.stats.models import Record
    ...

we had a similar problem here: https://github.com/django-daiquiri/daiquiri/blob/master/daiquiri/oai/adapter.py#L365

Also, I would add that to all Record.objects.create().

[kimakan]

Hi @jochenklar , thanks for the suggestion! I thought about adding this to every Record.objects.create() but in the end, it would not solve the dependency in the migrations, so I didn't do it.