Remove "gross hack" for py3pep8 env; run releasenotes under py3

Change-Id: Ib853f79bc062ec550627342d0fc5b2b92029f25c

tox.ini

@@ -106,21 +106,13 @@ basepython = python2.7
 commands =
   flake8 {posargs:swift test doc setup.py}
   flake8 --filename=swift* bin
+  python ./setup.py check --restructuredtext --strict
   bandit -c bandit.yaml -r swift -n 5
   ./.manpages {posargs}
 
 [testenv:py3pep8]
 basepython = python3
-install_command = echo {packages}
-whitelist_externals = echo
-commands =
-  # Gross hack. There's no other way to get it to /not/ install swift itself
-  # (which triggers installing eventlet) but also get flake8 installed.
-  pip install flake8
-  flake8 swift test doc setup.py
-  flake8 --filename=swift* bin
-  python ./setup.py check --restructuredtext --strict
-  ./.manpages {posargs}
+commands = {[testenv:pep8]commands}
 
 [testenv:func]
 basepython = python2.7
@@ -191,6 +183,7 @@ deps = bindep
 commands = bindep test
 
 [testenv:releasenotes]
+basepython = python3
 deps = -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -a -W -E -d releasenotes/build/doctrees -b html releasenotes/source releasenotes/build/html