Add tests docs to CI and fix docs warning (#238)

* Add tests docs to CI and fix docs warning

* Switch to storing environment variables in travis outside of secure vars.

* Force a rebuild.

* Force a rebuild.

* Run integration tests just once per test run.

* Minor updates.

* Nevermind; this test class covers more than just integration tests.

* Attempting to fix docs build via https://stackoverflow.com/questions/61711710/runtimeerror-class-not-set-defining-abstractbaseuser-as-class-django-co\#comment112739057_63045563

* Minor docs fix.

Co-authored-by: Adam Coddington <me@adamcoddington.net>

.travis.yml

@@ -3,6 +3,8 @@ os: linux
 language: python
 
 jobs:
+  - env: TOX_ENV=docs
+    python: 3.8
   # sort by django version, next to by python version
   # Django 1.11 support all supported Python interpreter
   - env: TOX_ENV=django111-py35
@@ -34,16 +36,9 @@ jobs:
     python: 3.6
   - env: TOX_ENV=django30-py37
     python: 3.7
-  - env: TOX_ENV=django30-py38
+  - env: TOX_ENV=django30-py38 INTEGRATION=1
     python: 3.8
 
-env:
-  global:
-    - secure: aswHU7pQroGM+GHoYlhXzzk2FYfqxXJORjqXPsbgoHAIu4Bssaj8+YAzIcdy3j9kSt4I8VBpjnn8H/wzQXki75JBZOosQrIeMK018+uR+ZMONBLqDYW/N7EJHLgZt9QXxQNKeZygrD4GN/Dc4gLHGvPQC/RfPuuHcnF0Liaahoo=
-    - secure: RZ6M6984P885GRoyx9n/WCCWGoFAzYpS8sZkXu3e/HK9oPXfaM2IEHjkq03jIC/FcWn/QMtFjOUBqQU94rnqdivFdFkeZHk1WUQgC0hztH3Qhh9zu2PNIrYUDpVD5dJqBpprWbSwFP8yNsJlP9A2RUubTlZblKHuaBhhiuNN+kU=
-    - secure: gsAAl/RaTodLJDHWOuHZWtooa9/psyXBONF7ElZOTki3WvH+KugtjuXn3pXBGbUhvGqd5qfgPqX7WQOFP9KTdkXBbkU20rCHLh3SV8V2vRkGFAFiGPBTFfSA83zFNMvmgEnTww4OzYsfs4wHTEyxBeQkggnB5bXEvqkFVrHBjuQ=
-    - secure: mMa7UUt+CQDB52fGM1T3oRL67OzQzRIc+BQCOqUEUhBV7p5g7Y1Hv6NTdVZTvK16x3DsP+5kFNd1v7rsTFw2qzP3hOxIv2BtMPuSzZdnN85Zd/nGwnztxzj/rqw7TMBaYvIdEZZbpRF/K0p0Xr6LJK2s9UkPXPUaLqly7kNi360=
-
 install:
   - pip install tox