Fix and reorganize tox env definitions

* Define py35 commands in a single place.
  Previously it was defined in [testenv] and [testenv:py35].
* py35 env should use python3.5 instead of python3
  because pyNN job is specific to a specific python version.
  In addition, python version is automatically assumed by tox.
* Sort env definitions in the order of unit tests, other testing stuffs
  with 'testenv:' prefix and finally non testenv stuffs (like flake8).
* Drop testenv:manage-py35dj20 because testenv:manage now uses
  python 3.5 and Django 2.0.
* Avoid using dict-style env commands definitions.
  In OpenStack projects, we usually use [testenv:xxxx] style.

Change-Id: Ib55031a50a51f952b738f0fdf33313fa2c7522ff

tox.ini

@@ -15,20 +15,17 @@ deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
   -r{toxinidir}/test-requirements.txt
   -r{toxinidir}/requirements.txt
+commands = {[unit_tests]commands}
+
+[unit_tests]
 commands =
-  horizon: {envpython} {toxinidir}/manage.py test --settings=horizon.test.settings {posargs}
-  py27: {[unit_tests]commands}
-  py35: {[unit_tests]commands}
-  openstack_dashboard: {envpython} {toxinidir}/manage.py test --settings=openstack_dashboard.test.settings {posargs}
-  runserver: {envpython} {toxinidir}/manage.py runserver {posargs}
-  venv: {posargs}
+    find . -type f -name "*.pyc" -delete
+    bash {toxinidir}/tools/unit_tests.sh {envpython} {toxinidir} {posargs}
 
 [testenv:py35]
-basepython = python3
 setenv =
   PYTHONUNBUFFERED = 1
   {[testenv]setenv}
-commands = {[unit_tests]commands}
 
 [testenv:py3-dj111]
 basepython = python3
@@ -36,10 +33,16 @@ commands =
   pip install django>=1.11,<2
   {[unit_tests]commands}
 
-[unit_tests]
-commands =
-    find . -type f -name "*.pyc" -delete
-    bash {toxinidir}/tools/unit_tests.sh {envpython} {toxinidir} {posargs}
+[testenv:lower-constraints]
+basepython = python3
+deps =
+  -c{toxinidir}/lower-constraints.txt
+  -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/requirements.txt
+
+[testenv:venv]
+basepython = python3
+commands = {posargs}
 
 [testenv:pep8]
 basepython = python3
@@ -52,6 +55,7 @@ commands =
   {envpython} {toxinidir}/manage.py extract_messages --verbosity 0 --check-only
   bash {toxinidir}/tools/find_executables.sh
   doc8 doc/source releasenotes/source releasenotes/notes
+  python setup.py check --restructuredtext --strict
 
 [testenv:cover]
 basepython = python3
@@ -149,12 +153,9 @@ basepython = python3
 deps =
 commands = {envpython} {toxinidir}/manage.py {posargs}
 
-[testenv:manage-py35dj20]
-basepython = python3.5
-deps = {[testenv:manage]deps}
-commands =
-  pip install django>=2.0,<2.1
-  {[testenv:manage]commands}
+[testenv:runserver]
+basepython = python3
+commands = {envpython} {toxinidir}/manage.py runserver {posargs}
 
 [flake8]
 filename = *.py,django.wsgi
@@ -186,12 +187,3 @@ max-line-length = 80
 # D000: Check RST validity
 # - cannot handle "none" for code-block directive
 ignore = D000
-
-[testenv:lower-constraints]
-basepython = python3
-deps =
-  -c{toxinidir}/lower-constraints.txt
-  -r{toxinidir}/test-requirements.txt
-  -r{toxinidir}/requirements.txt
-commands =
-  {[unit_tests]commands}