tox: Trivial cleanup

- Add some helpful descriptions for the various environments
- Use lower-case boolean values (they're prettier)
- Remove some unnecessary warning filters for issues not present on
  Python 3.6+
- Move the 'venv' target to the end of the file, indicating its priority
  (quite low)
- Fix a bit of wonky indentation

Change-Id: Ia083f959d2a9c974b4c0592fdada21dcc766dca4
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

tox.ini

@@ -1,25 +1,23 @@
 [tox]
 minversion = 3.1.1
 envlist = py36,py37,functional,pep8
-skipsdist = True
+skipsdist = true
 # Automatic envs (pyXX) will use the python version appropriate to that
 # env and ignore basepython inherited from [testenv]. That's what we
 # want, and we don't need to be warned about it.
-ignore_basepython_conflict = True
+ignore_basepython_conflict = true
 
 [testenv]
 basepython = python3
-usedevelop = True
+usedevelop = true
 whitelist_externals =
   rm
 setenv =
-   VIRTUAL_ENV={envdir}
-   PYTHONWARNINGS=ignore::DeprecationWarning:distutils,ignore::DeprecationWarning:site
-   PYTHONDONTWRITEBYTECODE=1
+  PYTHONDONTWRITEBYTECODE=1
 deps =
-   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
-   -r{toxinidir}/test-requirements.txt
-   -r{toxinidir}/requirements.txt
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/requirements.txt
 commands = stestr run {posargs}
 
 # NOTE(cdent): Do not set envdir here as it confuses tox-siblings.
@@ -55,18 +53,14 @@ commands =
   {[testenv:functional]commands}
 
 [testenv:pep8]
+description =
+  Run style checks.
 envdir = {toxworkdir}/shared
 commands = flake8 {posargs}
 
-[testenv:venv]
-commands = {posargs}
-# The docs requirements are included here for creating release notes, e.g.:
-#   tox -e venv -- reno new <slug>
-deps =
-  {[testenv]deps}
-  -r{toxinidir}/doc/requirements.txt
-
 [testenv:cover]
+description =
+  Run unit tests with coverage enabled.
 envdir = {toxworkdir}/shared
 setenv =
   {[testenv]setenv}
@@ -80,6 +74,8 @@ commands =
   coverage report
 
 [testenv:docs]
+description =
+  Build main documentation.
 deps =
   -r{toxinidir}/doc/requirements.txt
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
@@ -88,6 +84,8 @@ commands =
   sphinx-build -W -b html -d doc/build/doctrees doc/source doc/build/html
 
 [testenv:pdf-docs]
+description =
+  Build PDF documentation.
 deps = {[testenv:docs]deps}
 whitelist_externals =
   make
@@ -96,18 +94,28 @@ commands =
   make -C doc/build/pdf
 
 [testenv:releasenotes]
+description =
+  Build release notes.
 deps = {[testenv:docs]deps}
 commands =
   rm -rf releasenotes/build
   sphinx-build -W -b html -d releasenotes/build/doctrees releasenotes/source releasenotes/build/html
 
+[testenv:venv]
+commands = {posargs}
+# The docs requirements are included here for creating release notes, e.g.:
+#   tox -e venv -- reno new <slug>
+deps =
+  {[testenv]deps}
+  -r{toxinidir}/doc/requirements.txt
+
 [testenv:debug]
 commands = oslo_debug_helper {posargs}
 
 [flake8]
 # E123, E125 skipped as they are invalid PEP-8.
 # W503 line break before binary operator
-show-source = True
+show-source = true
 ignore = E123,E125,W503
 builtins = _
 exclude=.venv,.git,.tox,dist,doc,*lib/python*,*egg,build