Drop support for Django 3.1 (#1548)

* Drop support for Django 3.1

* Add mention of removing support for django 3.1 in change log.

Co-authored-by: Tim Schilling <[email protected]>

Author: hramezani

docs/changes.rst

@@ -4,6 +4,8 @@ Change log
 Next version
 ------------
 
+* Removed support for Django 3.1.
+
 3.2.4 (2021-12-15)
 ------------------
 

setup.cfg

@@ -15,7 +15,6 @@ classifiers =
     Environment :: Web Environment
     Framework :: Django
     Framework :: Django :: 2.2
-    Framework :: Django :: 3.1
     Framework :: Django :: 3.2
     Framework :: Django :: 4.0
     Intended Audience :: Developers

tox.ini

@@ -2,14 +2,13 @@
 envlist =
     docs
     packaging
-    py{36,37}-dj{22,31,32}-{sqlite,postgresql,postgis,mysql}
-    py{38,39}-dj{22,31,32,40,main}-{sqlite,postgresql,postgis,mysql}
+    py{36,37}-dj{22,32}-{sqlite,postgresql,postgis,mysql}
+    py{38,39}-dj{22,32,40,main}-{sqlite,postgresql,postgis,mysql}
     py{310}-dj{32,40,main}-{sqlite,postgresql,postgis,mysql}
 
 [testenv]
 deps =
     dj22: django~=2.2.17
-    dj31: django~=3.1.3
     dj32: django~=3.2.9
     dj40: django~=4.0.0
     sqlite: mock
@@ -43,25 +42,25 @@ whitelist_externals = make
 pip_pre = True
 commands = make coverage TEST_ARGS='{posargs:tests}'
 
-[testenv:py{36,37,38,39,310}-dj{22,31,32,40,main}-postgresql]
+[testenv:py{36,37,38,39,310}-dj{22,32,40,main}-postgresql]
 setenv =
     {[testenv]setenv}
     DB_BACKEND = postgresql
     DB_PORT = {env:DB_PORT:5432}
 
-[testenv:py{36,37,38,39,310}-dj{22,31,32,40,main}-postgis]
+[testenv:py{36,37,38,39,310}-dj{22,32,40,main}-postgis]
 setenv =
     {[testenv]setenv}
     DB_BACKEND = postgis
     DB_PORT = {env:DB_PORT:5432}
 
-[testenv:py{36,37,38,39,310}-dj{22,31,32,40,main}-mysql]
+[testenv:py{36,37,38,39,310}-dj{22,32,40,main}-mysql]
 setenv =
     {[testenv]setenv}
     DB_BACKEND = mysql
     DB_PORT = {env:DB_PORT:3306}
 
-[testenv:py{36,37,38,39,310}-dj{22,31,32,40,main}-sqlite]
+[testenv:py{36,37,38,39,310}-dj{22,32,40,main}-sqlite]
 setenv =
     {[testenv]setenv}
     DB_BACKEND = sqlite3