Clean requirements, add pip check job

Removes redundant requirements and adds a new job which runs
'tox -epip-check-reqs' in order to avoid having redundant
dependencies specified or missing some.

Change-Id: I5ca35922213cfbe4c2b4b49388bffcc0b8fc6a96

.zuul.yaml

@@ -8,6 +8,7 @@
       jobs:
         - refstack-tox-functional:
             nodeset: openstack-single-node-bionic
+        - refstack-tox-pip-check-reqs
     gate:
       jobs:
         - refstack-tox-functional:
@@ -25,3 +26,16 @@
       - ^releasenotes/.*$
     vars:
       tox_envlist: functional
+
+- job:
+    name: refstack-tox-pip-check-reqs
+    parent: openstack-tox
+    description: |
+      Run pip-extra-reqs and pip-missing-reqs to find any missing or redundant
+      dependencies. Uses tox with the ``pip-check-reqs`` environment.
+    irrelevant-files:
+      - ^.*\.rst$
+      - ^doc/.*$
+      - ^releasenotes/.*$
+    vars:
+      tox_envlist: pip-check-reqs

requirements.txt

@@ -8,7 +8,6 @@ oslo.config>=1.6.0 # Apache-2.0
 oslo.db>=1.4.1 # Apache-2.0
 oslo.log>=3.11.0
 oslo.utils>=3.16.0 # Apache-2.0
-six>=1.9.0 # MIT
 pecan>=0.8.2
 requests>=2.2.0,!=2.4.0
 requests-cache>=0.4.9,<0.6.0

tox.ini

@@ -69,8 +69,9 @@ exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build
 deps = pip_check_reqs
        -r{toxinidir}/requirements.txt
 commands=
-    pip-extra-reqs -d --ignore-file=refstack/tests/* refstack
-    pip-missing-reqs -d --ignore-file=refstack/tests/* refstack
+    # PyMySQL is a python only runtime dep if using MySQL
+    pip-extra-reqs -d --ignore-file=refstack/tests/* --ignore-requirement=PyMySQL refstack tools
+    pip-missing-reqs -d --ignore-file=refstack/tests/* refstack tools
 
 [testenv:debug]
 commands = oslo_debug_helper -t refstack/tests/unit {posargs}