Use pytest as our test runner for better parallelism

Also rewrote some asset tests to be in the pytest style. May do some more. Some warnings cleaned up in the process.

.github/workflows/django.yml

@@ -14,13 +14,7 @@ jobs:
     if: "!contains(github.event.head_commit.message, '[ci skip]')"
     strategy:
       matrix:
-        test-group: ["RIGS.tests.test_unit RIGS.tests.test_models RIGS.tests.test_functional", "versioning.tests.test_versioning", "users.tests.test_users"]
-        parallel: [true]
-        include:
-            - test-group: "assets.tests.test_assets"
-              parallel: false
-            - test-group: "RIGS.tests.test_interaction"
-              parallel: false
+        test-group: ["RIGS/tests/", "versioning/tests/", "users/tests/", "assets/tests/"]
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python
@@ -52,17 +46,14 @@ jobs:
           python manage.py check
           python manage.py makemigrations --check --dry-run
       - name: Run Tests
-        if: \!${{ matrix.parallel }}
-        run: coverage run manage.py test ${{ matrix.test-group }} --verbosity=2
+        if: ${{ matrix.parallel }}
+        run: coverage run -m pytest -n 8 ${{ matrix.test-group }}
       - uses: actions/upload-artifact@v2
-        if: failure() # Screenshots only make sense for the non-parallel, i.e. interaction tests anyway
+        if: failure()
         with:
             name: failure-screenshots ${{ matrix.test-group }}
             path: screenshots/
             retention-days: 5
-      - name: Run Tests (Parallel)
-        if: ${{ matrix.parallel }}
-        run: coverage run manage.py test ${{ matrix.test-group }} --parallel --verbosity=2
       - name: Upload Coverage
         run: coveralls --service=github
         env: