Add support for Django 3.0.x

[adamghill]

No description provided.

[AdrienLemaire]

@stphivos can you verify and merge this PR? django-mock-queries is now the only package in my project not supporting Django 3.

[stphivos]

Hi @adamghill I had to fix master in #108 for new builds to pass as the dependencies were broken. Can you pls rebase your PR? Thanks

[adamghill]

I ended up merging master into my branch, but 2.7 is breaking. It appears to be failing because it can't install drf?

https://travis-ci.org/stphivos/django-mock-queries/jobs/649088219

ERROR: Could not find a version that satisfies the requirement djangorestframework>=3.11 (from django-mock-queries==2.1.3) (from versions: 0.1, 0.1.1, 0.2.0, 0.2.1, 0.2.2, 0.2.3, 0.2.4, 0.3.0, 0.3.1, 0.3.2, 0.3.3, 0.4.0, 2.0.0, 2.0.1, 2.0.2, 2.1.0, 2.1.1, 2.1.2, 2.1.3, 2.1.4, 2.1.5, 2.1.6, 2.1.7, 2.1.8, 2.1.9, 2.1.10, 2.1.11, 2.1.12, 2.1.13, 2.1.14, 2.1.15, 2.1.16, 2.1.17, 2.2.0, 2.2.1, 2.2.2, 2.2.3, 2.2.4, 2.2.5, 2.2.6, 2.2.7, 2.3.0, 2.3.1, 2.3.2, 2.3.3, 2.3.4, 2.3.5, 2.3.6, 2.3.7, 2.3.8, 2.3.9, 2.3.10, 2.3.11, 2.3.12, 2.3.13, 2.3.14, 2.4.0, 2.4.1, 2.4.2, 2.4.3, 2.4.4, 2.4.5, 2.4.6, 2.4.8, 3.0.0, 3.0.1, 3.0.2, 3.0.3, 3.0.4, 3.0.5, 3.1.0, 3.1.1, 3.1.2, 3.1.3, 3.2.0, 3.2.1, 3.2.2, 3.2.3, 3.2.4, 3.2.5, 3.3.0, 3.3.1, 3.3.2, 3.3.3, 3.4.0, 3.4.1, 3.4.2, 3.4.3, 3.4.4, 3.4.5, 3.4.6, 3.4.7, 3.5.0, 3.5.1, 3.5.2, 3.5.3, 3.5.4, 3.6.0, 3.6.1, 3.6.2, 3.6.3, 3.6.4, 3.7.0, 3.7.1, 3.7.2, 3.7.3, 3.7.4, 3.7.5, 3.7.6, 3.7.7, 3.8.0, 3.8.1, 3.8.2, 3.9.0, 3.9.1, 3.9.2, 3.9.3, 3.9.4)

ERROR: No matching distribution found for djangorestframework>=3.11 (from django-mock-queries==2.1.3)

[stphivos]

Django 3.0.3 requires at least python 3.6.

Also django-rest-framework 3.10 or later supports Django 3.0.3. So travis and tox should reflect that:

tox.ini:

# Define supported tox env combinations using the codes below:
envlist =
    py{27,35}-dj{18,19,110}-drf33
    py{27,35,36,37}-dj{111}-drf{37,39}
    py{35,36,37}-dj{20,21,22}-drf{37,39}
    py{36,37}-dj{30}-drf{drf310}          <= Added django 3.0 here (in .travis.yml it's clearer which combinations run)

...

# Define pip requirement code to actual version mapping
[testenv]
deps =
    -rrequirements/dev.txt
    dj18: Django~=1.8.17
    dj19: Django~=1.9.12
    dj110: Django~=1.10.5
    dj111: Django~=1.11.17
    dj20: Django~=2.0.2
    dj21: Django~=2.1.0
    dj22: Django~=2.2.1
    dj30: Django~=3.0.3                   <= When referring to dj30, then Django~=3.0.3 will be installed
    drf33: djangorestframework~=3.3.2
    drf37: djangorestframework~=3.7.7
    drf39: djangorestframework~=3.9.2

.travis.yml:

    - python: 3.6
      env:
      ...
      - TOX_ENV=py36-dj22-drf39
      - TOX_ENV=py36-dj30-drf310
    - python: 3.7
      env:
      ...
      - TOX_ENV=py37-dj22-drf39
      - TOX_ENV=py37-dj30-drf310

For example, for TOX_ENV=py36-dj30-drf310, travis will install:

-rrequirements/dev.txt, Django~=3.0.3, djangorestframework~=3.10.3

I removed version ranges from requirements/core.txt so the library can be installed with future versions without issues. We just have to add them to the build matrix in order to verify they are compatible.