Introduce a new tox target that checks requirements.txt

That new tox target checks that we don't have missing requirements in
requirements.txt AND that we don't have superfluous (unused) requirements
in requirements.txt.

That patch is copy/pasted from I014375a5ecfebc723541c2f2db6c2e0fba636aa2
which tried to do the same for Nova (unmerged yet for an unknown reason).

This change also includes the fixes to requirements.txt needed
to pass the new tests.

Change-Id: Iff37af95269c38e4d435a53a21e5d60e2c5a3fa8

requirements.txt

@@ -10,7 +10,6 @@ netaddr!=0.7.16,>=0.7.13 # BSD
 testrepository>=0.0.18 # Apache-2.0/BSD
 oslo.concurrency>=3.8.0 # Apache-2.0
 oslo.config>=3.14.0 # Apache-2.0
-oslo.i18n>=2.1.0 # Apache-2.0
 oslo.log>=3.11.0 # Apache-2.0
 oslo.serialization>=1.10.0 # Apache-2.0
 oslo.utils>=3.16.0 # Apache-2.0
@@ -18,8 +17,10 @@ six>=1.9.0 # MIT
 fixtures>=3.0.0 # Apache-2.0/BSD
 testscenarios>=0.4 # Apache-2.0/BSD
 PyYAML>=3.1.0 # MIT
+python-subunit>=0.0.18 # Apache-2.0/BSD
 stevedore>=1.16.0 # Apache-2.0
 PrettyTable<0.8,>=0.7 # BSD
 os-testr>=0.7.0 # Apache-2.0
 urllib3>=1.15.1 # MIT
 debtcollector>=1.2.0 # Apache-2.0
+unittest2  # BSD

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = pep8,py35,py34,py27
+envlist = pep8,py35,py34,py27,pip-check-reqs
 minversion = 2.3.1
 skipsdist = True
 
@@ -158,3 +158,14 @@ exclude = .git,.venv,.tox,dist,doc,*egg
 
 [testenv:releasenotes]
 commands = sphinx-build -a -E -W -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html
+
+[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=tempest/tests/* tempest
+    pip-missing-reqs -d --ignore-file=tempest/tests/* tempest