test against Django master

.travis.yml

@@ -44,6 +44,8 @@ matrix:
      python: 3.6
    - env: TOXENV=py36-dj21-postgres-noelasticsearch
      python: 3.6
+   - env: TOXENV=py36-djmaster-postgres-noelasticsearch
+     python: 3.6
    - env: TOXENV=py36-dj111-postgres-elasticsearch2 INSTALL_ELASTICSEARCH2=yes
      python: 3.6
      sudo: true
@@ -83,6 +85,8 @@ matrix:
     - env: TOXENV=py36-dj111-postgres-elasticsearch6 INSTALL_ELASTICSEARCH6=yes
     - env: TOXENV=py36-dj20-postgres-elasticsearch6 INSTALL_ELASTICSEARCH6=yes
     - env: TOXENV=py36-dj21-postgres-elasticsearch6 INSTALL_ELASTICSEARCH6=yes
+    # allow failures against Django master
+    - env: TOXENV=py36-djmaster-postgres-noelasticsearch
 
 
 # Services

tox.ini

@@ -2,7 +2,7 @@
 skipsdist = True
 usedevelop = True
 
-envlist = py{34,35,36}-dj{111,20}-{sqlite,postgres,mysql,mssql}-{elasticsearch6,elasticsearch5,elasticsearch2,noelasticsearch},
+envlist = py{34,35,36}-dj{111,20,master}-{sqlite,postgres,mysql,mssql}-{elasticsearch6,elasticsearch5,elasticsearch2,noelasticsearch},
 
 [flake8]
 # D100: Missing docstring in public module
@@ -44,6 +44,7 @@ deps =
     dj111-mssql: django-pyodbc-azure==1.11.0.0
     dj20: Django>=2.0,<2.1
     dj21: Django>=2.1,<2.2
+    djmaster: dj21: git+https://github.com/django/django.git@master#egg=Django
 
     postgres: psycopg2>=2.6
     mysql: mysqlclient>=1.3.7,<1.4