tox: Remove dead settings/targets

The sdist target is useless given that releases are automated.
Similarly, the '[testenv] install_command' uses the default value and is
therefore not required. Finally, some other things were slightly off or
otherwise annoying and can be fixed.

Change-Id: Ia029aba9ee5bc79cf39043a5fcaf9463aa1518f7
Signed-off-by: Stephen Finucane <stephenfin@redhat.com>

tox.ini

@@ -1,30 +1,23 @@
 [tox]
-envlist = pep8,docs,py27,py37,py36,py35,py34
+envlist = pep8,docs,py27,py3{4,5,6,7}
 
 [testenv]
-install_command = pip install -U {opts} {packages}
-setenv =
-    VIRTUAL_ENV={envdir}
-
 commands =
   python -m git_review.tests.check_test_id_hashes discover --list
   python -m git_review.tests.prepare
   python setup.py testr --slowest --testr-args='--concurrency=2 {posargs}'
 
 deps =
-    -r{toxinidir}/requirements.txt
-    -r{toxinidir}/test-requirements.txt
+  -r{toxinidir}/requirements.txt
+  -r{toxinidir}/test-requirements.txt
 
 [testenv:pep8]
 commands = flake8
 
-[testenv:sdist]
-commands = python setup.py sdist {posargs}
-
 [testenv:docs]
 deps =
-    -r{toxinidir}/requirements.txt
-    -r{toxinidir}/doc/requirements.txt
+  -r{toxinidir}/requirements.txt
+  -r{toxinidir}/doc/requirements.txt
 commands =
   sphinx-build -W -d doc/build/doctrees -b html doc/source/ doc/build/html
 
@@ -34,4 +27,4 @@ commands = {posargs}
 [flake8]
 ignore = E125,H202,H405,H904
 show-source = True
-exclude = .venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build
+exclude = .venv,.git,.tox,dist,doc,releasenotes,*lib/python*,*egg,build