Update Travis matrix to allow failures on Django master

Signed-off-by: Aleksi Häkli <aleksi.hakli@iki.fi>

.travis.yml

@@ -14,6 +14,11 @@ matrix:
   exclude:
     - python: 3.5
       env: DJANGO=master
+  allow_failures:
+    - python: 3.6
+      env: DJANGO=master
+    - python: 3.7
+      env: DJANGO=master
 install: pip install tox-travis codecov
 script: tox
 after_success:

tox.ini

@@ -24,8 +24,6 @@ deps =
     django21: django>=2.1,<2.2
     djangomaster: https://github.com/django/django/archive/master.tar.gz
 usedevelop = True
-ignore_outcome =
-    djangomaster: True
 commands =
     pytest
     prospector