update python django (#432)

* update python django
add django 3.1 to test
drop eol python 3.5
add python 3.9

.travis.yml

@@ -1,10 +1,10 @@
 language: python
 cache: pip
 python:
-- 3.5
 - 3.6
 - 3.7
 - 3.8
+- 3.9
 - pypy3
 install: pip install tox-travis
 script: tox

setup.py

@@ -36,6 +36,7 @@ setup(
         'Framework :: Django',
         'Framework :: Django :: 2.2',
         'Framework :: Django :: 3.0',
+        'Framework :: Django :: 3.1',
         'Intended Audience :: Developers',
         'License :: OSI Approved :: BSD License',
         'Natural Language :: English',
@@ -45,6 +46,7 @@ setup(
         'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
+        'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3 :: Only',
         'Programming Language :: Python :: Implementation :: CPython',
         'Programming Language :: Python :: Implementation :: PyPy',
@@ -53,6 +55,7 @@ setup(
     packages=find_packages(exclude=['tests', 'tests.*']),
     include_package_data=True,
     zip_safe=False,
+    python_requires='>=3.6',
     extras_require={
         'database': ['django-picklefield'],
         'redis': ['redis'],

tox.ini

@@ -1,8 +1,8 @@
 [tox]
 envlist =
-    py{35,36,37,pypy3}-django{22}-unittest
-    py{36,37,38}-django{30,-master}-unittest
-    py{36,37,38,pypy3}-django{22,30,-master}-pytest
+    py{36,37,38,39,pypy3}-django{22}-unittest
+    py{36,37,38,39,pypy3}-django{30,31,-master}-unittest
+    py{36,37,38,39,pypy3}-django{22,30,31,-master}-pytest
 
 [testenv]
 deps =
@@ -12,6 +12,7 @@ deps =
     django-picklefield
     django-22: Django>=2.2,<3.0
     django-30: Django>=3.0,<3.1
+    django-31: Django>=3.1,<3.2
     django-master: https://github.com/django/django/archive/master.tar.gz
     pytest: pytest
     pytest: pytest-cov