Make the Travis CI matrix explicit, add newer Python and Django versions

.travis.yml

@@ -1,25 +1,50 @@
-language: python
+dist: xenial
 sudo: false
+language: python
 cache: pip
 python:
-  - "3.6"
-  - "3.5"
-env:
-  - REQ='Django>=2.1,<2.2'
-  - REQ='Django>=2.0,<2.1'
+  - 3.7
+services:
+  - postgresql
+# Matrix composition:
+# Django LTS versions: All supported Python releases
+# Other versions and master branch: The newest possible Python release
 matrix:
-install:
-  - pip install -U pip setuptools wheel
-  - pip install $REQ
-  - python setup.py install
-script: cd tests && ./manage.py test -v 2 testapp && cd ..
-
-jobs:
+  fast_finish: true
   include:
-    - stage: style
-      env: REQ=none
-      install: skip
-      script:
+    - python: 3.7
+      env: REQ="https://github.com/django/django/archive/master.zip#egg=Django"
+    - python: 3.7
+      env: REQ="Django>=3.0,<3.1"
+    - python: 3.6
+      env: REQ="Django>=3.0,<3.1"
+    - python: 3.7
+      env: REQ="Django>=2.2,<3.0"
+    - python: 3.6
+      env: REQ="Django>=2.2,<3.0"
+    - python: 3.5
+      env: REQ="Django>=2.2,<3.0"
+    - python: 3.7
+      env: REQ="Django>=2.1,<2.2"
+    - python: 3.7
+      env: REQ="Django>=2.0,<2.1"
+    - python: 3.7
+      env: REQ="Django>=1.11,<2.0"
+    - python: 3.6
+      env: REQ="Django>=1.11,<2.0"
+    - python: 3.5
+      env: REQ="Django>=1.11,<2.0"
+    - python: 3.7
+      env: REQ="black flake8"
+      install:
         - pip install black flake8
+      script:
         - flake8 .
         - black --check spark tests
+  allow_failures:
+    - env: REQ="https://github.com/django/django/archive/master.zip#egg=Django"
+install:
+- pip install -U pip setuptools wheel
+- pip install $REQ
+- python setup.py install
+script: cd tests && ./manage.py test -v 2 testapp && cd ..

CHANGELOG.rst

@@ -18,6 +18,8 @@ Change log
   ``spark_mails`` API and made mail sending not fail silently by
   default.
 - Fixed a bug where an empty template would crash the mail rendering.
+- Rewrote the Travis CI configuration to make jobs explicit, added newer
+  Django and Python versions to the matrix.
 
 
 `0.3`_ (2018-10-29)

tox.ini

@@ -26,4 +26,4 @@ changedir = {toxinidir}
 skip_install = true
 commands =
     coverage run tests/manage.py test -v 2 {posargs:testapp}
-    coverage html
+    coverage report -m