Fix harvest error with requires_model_validation

[nikolas]

Addresses this error I ran into with the new 0.2.23 release, introduced in the django 1.9 changes #522:

File
"/home/travis/build/ccnmtl/mediathread/ve/lib/python2.7/site-packages/django/core/management/base.py",
line 265, in init

 '"requires_system_checks".' % self.__class__.__name__)

django.core.exceptions.ImproperlyConfigured: Command Command defines
both "requires_model_validation" and "requires_system_checks", which is
illegal. Use only "requires_system_checks".
make: *** [harvest1] Error 1

[m-vdb]

Ah my bad, I saw that only in this PR: #527 (cf. my comment on it)

[m-vdb]

the actual fix I made is 842d184

[nikolas]

@gabrielfalcao lettuce is broken in Django 1.8 under the 0.2.23 release. Please merge this!

[michelts]

+1

[michelts]

@nikolas and @m-vdb it would be interesting to make tox run in different versions of django too, so the tests would catch any error. I think the tox file should include something like that:

envlist = py27-django{18,19,110,111}

[testenv]
deps =
    django18: Django>=1.8,<1.9
    django19: Django>=1.9,<1.10
    django110: Django>=1.10,<1.11
    django111: Django>=1.11,<2

Maybe the requirements loaded during tests should strip out django to let the tox file define it. I can help you need. Tell me if you want I make a PR to your own #525 and #551 pull requests.

[nikolas]

@michelts yeah, i have a ticket for that here: #530

[skorokithakis]

If someone can resolve the conflicts on this, I can merge.