Start testing with Django 3.1 b/c it was released today

.travis.yml

@@ -19,6 +19,7 @@ matrix:
   include:
     - { stage: django_not_installed, python: 3.6, env: TOXENV=django_not_installed }
     - { stage: django_is_installed, python: 3.6, env: TOXENV=django_is_installed }
+    - { stage: test, python: 3.8, env: DJANGO=3.1 }
     - { stage: test, python: 3.6, env: DJANGO=3.0 }
     - { stage: test, python: 3.6, env: DJANGO=2.0 }
     - { stage: test, python: 3.6, env: DJANGO=1.11 }

tox.ini

@@ -10,7 +10,7 @@ envlist =
     readme
     py{36}-django{111,20,-master}
     py{35,36,37}-django22
-    py{36,37,38}-django30
+    py{36,37,38}-django{30,31}
 
 [testenv]
 commands =
@@ -21,7 +21,7 @@ commands =
     readme: bash -c \'python setup.py -q sdist && twine check dist/*\'
     py{36}-django{111,20,-master}: coverage run pylint_django/tests/test_func.py -v
     py{35,36,37}-django22: coverage run pylint_django/tests/test_func.py -v
-    py{36,37,38}-django30: coverage run pylint_django/tests/test_func.py -v
+    py{36,37,38}-django{30,31}: coverage run pylint_django/tests/test_func.py -v
     clean: find . -type f -name '*.pyc' -delete
     clean: find . -type d -name __pycache__ -delete
     clean: rm -rf build/ .cache/ dist/ .eggs/ pylint_django.egg-info/ .tox/
@@ -36,6 +36,7 @@ deps =
     django21: Django>=2.1,<2.2
     django22: Django>=2.2,<3.0
     django30: Django>=3.0,<3.1
+    django31: Django>=3.1,<3.2
     django-master: Django
     django-master: git+https://github.com/pycqa/astroid@master
     django-master: git+https://github.com/pycqa/pylint@master
@@ -47,7 +48,7 @@ whitelist_externals =
     readme: bash
     py{36}-django{111,20,-master}: coverage
     py{35,36,37}-django22: coverage
-    py{36,37,38}-django30: coverage
+    py{36,37,38}-django{30,31}: coverage
     clean: find
     clean: rm
 
@@ -58,6 +59,7 @@ DJANGO =
     2.1: django21
     2.2: django22
     3.0: django30
+    3.1: django31
     master: django-master
 
 [flake8]