update tox

tox.ini

@@ -1,7 +1,7 @@
 [tox]
 envlist =
     {2.7,3.5,3.6,3.7,3.8,pypy,pypy3}-unit
-    {2.7,3.5,3.6,3.7,3.8,pypy,pypy3}-integration-{rabbitmq,redis,dynamodb,azureblockblob,cache,cassandra}
+    {2.7,3.5,3.6,3.7,3.8,pypy,pypy3}-integration-{rabbitmq,redis,dynamodb,azureblockblob,cassandra}
 
     flake8
     apicheck
@@ -35,9 +35,6 @@ setenv =
     WORKER_LOGLEVEL = INFO
     PYTHONIOENCODING = UTF-8
 
-    cache: TEST_BROKER=pyamqp://
-    cache: TEST_BACKEND=cache+pylibmc://
-
     cassandra: TEST_BROKER=pyamqp://
     cassandra: TEST_BACKEND=cassandra://
 
@@ -65,7 +62,7 @@ basepython =
     3.8: python3.8
     pypy: pypy
     pypy3: pypy3
-    flake8,apicheck,linkcheck,configcheck,pydocstyle,bandit: python3.7
+    flake8,apicheck,linkcheck,configcheck,pydocstyle,bandit: python3.8
     flakeplus: python2.7
 usedevelop = True
 install_command = {toxinidir}/tox_install_command.sh {opts} {packages}