Introduce pip-check-reqs task to tox

This commit introduces pip-check-reqs task to tox.ini. We should avoid
inconsistency between (test-)requirements.txt and actual source code.

Change-Id: I9d734cdbc1c1fb3283835890b8132e54a7b757d7

requirements.txt

@@ -6,6 +6,3 @@ pbr>=1.6
 SQLAlchemy>=0.8.2
 alembic>=0.4.1
 oslo.config>=1.4.0.0a3
-Babel>=1.3,!=2.3.0,!=2.3.1,!=2.3.2,!=2.3.3  # BSD
-stevedore>=1.3.0
-six>=1.5.2

test-requirements.txt

@@ -18,3 +18,4 @@ psycopg2
 os-testr
 reno>=0.1.1 # Apache2
 oslo.concurrency>=3.5.0
+six>=1.5.2

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 minversion = 2.0
-envlist = py35,py27,pypy,pep8
+envlist = py35,py27,pypy,pep8,pip-check-reqs
 skipsdist = True
 
 [testenv]
@@ -46,3 +46,15 @@ show-source = True
 ignore = E123,E125,E129,H305,H402,E711
 builtins = _
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build,releasenotes
+
+
+[testenv:pip-check-reqs]
+# Do not install test-requirements as that will pollute the virtualenv for
+# determining missing packages.
+# This also means that pip-check-reqs must be installed separately, outside
+# of the requirements.txt files
+deps = pip_check_reqs
+       -r{toxinidir}/requirements.txt
+commands=
+    pip-extra-reqs -d --ignore-file=coverage2sql/tests/* coverage2sql
+    pip-missing-reqs -d --ignore-file=coverage2sql/tests/* coverage2sql