Update tested Python & Django versions

Replaces `django.utils.six` with `six` to support newer Django versions.

Updates Tox config to:
- remove unsupported Django versions
- add pypy3
- add Django 2.2
- update djmaster Python versions

configurations/base.py

@@ -1,7 +1,7 @@
 import os
 import re
+import six
 
-from django.utils import six
 from django.conf import global_settings
 from django.core.exceptions import ImproperlyConfigured
 

configurations/utils.py

@@ -1,10 +1,10 @@
 import inspect
+import six
 import sys
 
 from importlib import import_module
 
 from django.core.exceptions import ImproperlyConfigured
-from django.utils import six
 
 
 def isuppercase(name):

configurations/values.py

@@ -2,11 +2,11 @@ import ast
 import copy
 import decimal
 import os
+import six
 import sys
 
 from django.core import validators
 from django.core.exceptions import ValidationError, ImproperlyConfigured
-from django.utils import six
 
 from .utils import import_by_path, getargspec
 

setup.py

@@ -41,6 +41,7 @@ setup(
             'django-cadmin = configurations.management:execute_from_command_line',
         ],
     },
+    install_requires=['six'],
     extras_require={
         'cache': ['django-cache-url'],
         'database': ['dj-database-url'],
@@ -53,7 +54,6 @@ setup(
             'dj-database-url',
             'dj-email-url',
             'dj-search-url',
-            'six',
             'Sphinx>=1.4',
         ],
     },

tests/settings/main.py

@@ -31,7 +31,6 @@ class Test(Configuration):
         'django.contrib.contenttypes',
         'django.contrib.sites',
         'django.contrib.auth',
-        'django.contrib.admin',
         'tests',
     ]
 

tests/urls.py

@@ -1,6 +1,2 @@
-from django.conf.urls import url
-from django.contrib import admin
-
 urlpatterns = [
-    url(r'^admin/', admin.site.urls),
 ]

tox.ini

@@ -6,9 +6,10 @@ whitelist_externals = sphinx-build
 envlist =
     checkqa,
     readme-py27,
-    py{27,34,35,36,py}-dj{18,110,111}
+    py{27,34,35,36,py}-dj111
-    py{34,35,36,37}-dj20
+    py{34,35,36,37,py3}-dj20
-    py{35,36,37}-dj{21,master}
+    py{35,36,37,py3}-dj{21,22}
+    py{36,37,38,py3}-dj{30,master}
 
 [testenv]
 usedevelop = true
@@ -18,11 +19,11 @@ setenv =
     coverage: COVERAGE_PROCESS_START = {toxinidir}/setup.cfg
     coverage: _TEST_RUN_PREFIX=coverage run
 deps =
-    dj18: django>=1.8,<1.9
-    dj110: django>=1.10,<1.11
     dj111: django>=1.11,<2.0
     dj20: django>=2.0a1,<2.1
     dj21: django>=2.1a1,<2.2
+    dj22: django>=2.2a1,<3.0
+    dj30: django>=3.0a1<3.1
     djmaster: https://github.com/django/django/archive/master.tar.gz#egg=django
     py27,pypy: mock
     coverage: coverage