Test with postgresql and mariadb on multiple versions of Django.

tox.ini

@@ -3,18 +3,21 @@ envlist =
     flake8
     style
     readme
-    py{35,36,37}-dj111
-    py{35,36,37,38}-dj22
-    py{36,37,38}-dj30
-    py{36,37,38}-djmaster
-    postgresql
-    mariadb
+    py{35,36,37}-dj111-sqlite
+    py{35,36,37,38}-dj22-sqlite
+    py{36,37,38}-dj30-sqlite
+    py{36,37,38}-djmaster-sqlite
+    py37-dj111-{postgresql,mariadb}
+    py{37,38}-dj{22,30}-{postgresql,mariadb}
 
 [testenv]
 deps =
     dj111: Django==1.11.*
     dj22: Django==2.2.*
     dj30: Django==3.0.*
+    sqlite: mock
+    postgresql: psycopg2-binary
+    mariadb: mysqlclient
     djmaster: https://github.com/django/django/archive/master.tar.gz
     coverage
     Jinja2
@@ -23,38 +26,8 @@ deps =
     sqlparse
 setenv =
     PYTHONPATH = {toxinidir}
-whitelist_externals = make
-pip_pre = True
-commands = make coverage TEST_ARGS='{posargs:tests}'
-
-[testenv:postgresql]
-deps =
-    Django==1.11.*
-    coverage
-    Jinja2
-    html5lib
-    psycopg2-binary
-    selenium<4.0
-    sqlparse
-setenv =
-    PYTHONPATH = {toxinidir}
-    DJANGO_DATABASE_ENGINE = postgresql
-whitelist_externals = make
-pip_pre = True
-commands = make coverage TEST_ARGS='{posargs:tests}'
-
-[testenv:mariadb]
-deps =
-    Django==2.2.*
-    coverage
-    Jinja2
-    html5lib
-    mysqlclient<1.4
-    selenium<4.0
-    sqlparse
-setenv =
-    PYTHONPATH = {toxinidir}
-    DJANGO_DATABASE_ENGINE = mysql
+    postgresql: DJANGO_DATABASE_ENGINE = postgresql
+    mariadb: DJANGO_DATABASE_ENGINE = mysql
 whitelist_externals = make
 pip_pre = True
 commands = make coverage TEST_ARGS='{posargs:tests}'