Remove duplicated optional dependencies from test requirements

... and use extras to define these, instead.

Change-Id: I6f04f5d09cffc825d336d5a11bf27370bbf69004
Signed-off-by: Takashi Kajinami <kajinamit@oss.nttdata.com>

doc/requirements.txt

@@ -1,22 +1,3 @@
 sphinx>=2.0.0 # BSD
 openstackdocstheme>=2.2.1 # Apache-2.0
 reno>=3.1.0 # Apache-2.0
-
-# Install dependencies for tooz so that autodoc works.
-## etcd3gw
-etcd3gw>=0.1.0 # Apache-2.0
-## redis
-redis>=3.1.0 # MIT
-## postgresql
-psycopg2>=2.5 # LGPL/ZPL
-## mysql
-PyMySQL>=0.6.2 # MIT License
-## zookeeper
-kazoo>=2.2 # Apache-2.0
-## memcached
-pymemcache>=1.2.9 # Apache 2.0 License
-## ipc
-sysv-ipc>=0.6.8 # BSD License
-## kubernetes
-sherlock>=0.4.1 # MIT License
-kubernetes>=2.8.1 # Apache-2.0

test-requirements.txt

@@ -5,12 +5,3 @@ pifpaf>=0.10.0 # Apache-2.0
 stestr>=2.0.0
 ddt>=1.2.1 # MIT
 requests>=2.10.0 # Apache-2.0
-etcd3gw>=2.3.0 # Apache-2.0
-redis>=4.0.0 # MIT
-psycopg2>=2.5 # LGPL/ZPL
-PyMySQL>=0.6.2 # MIT License
-kazoo>=2.6 # Apache-2.0
-pymemcache>=1.2.9 # Apache 2.0 License
-sysv-ipc>=0.6.8 # BSD License
-kubernetes>=2.8.1 # Apache-2.0
-sherlock>=0.4.1 # MIT License

tox.ini

@@ -8,6 +8,15 @@ constraints =
 deps =
   -r{toxinidir}/requirements.txt
   -r{toxinidir}/test-requirements.txt
+extras =
+  etcd3gw
+  redis
+  postgresql
+  mysql
+  zookeeper
+  memcached
+  ipc
+  kubernetes
 setenv =
   TOOZ_TEST_URLS = file:///tmp ipc://
   zookeeper: TOOZ_TEST_DRIVERS = zookeeper
@@ -57,9 +66,10 @@ commands =
   sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:releasenotes]
+skip_install = true
 deps = {[testenv:docs]deps}
 commands =
-    sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
+  sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
 
 [testenv:pep8]
 description =