Modernize tox.ini

The -constraints venvs have gone away and constraints are just the
default setting. Also updates the list of default envs.

Change-Id: I8c442df1cacf6077febc6e26b66d134496ae7a3c

tox.ini

@@ -1,39 +1,27 @@
 [tox]
 minversion = 1.8
-envlist = py34-constraints,py27-constraints,pypy-constraints,pep8-constraints
+envlist = py35,py27,pep8
 skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command =
-                  constraints: {[testenv:common-constraints]install_command}
-                  pip install -U {opts} {packages}
+install_command = pip install {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
-deps = -r{toxinidir}/test-requirements.txt
+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 = stestr run --slowest {posargs}
 
-[testenv:common-constraints]
-install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
-
 [testenv:pep8]
 basepython = python3
 commands = flake8 {posargs}
 
-[testenv:pep8-constraints]
-basepython = python3
-install_command = {[testenv:common-constraints]install_command}
-commands = flake8 {posargs}
-
 [testenv:venv]
 basepython = python3
 commands = {posargs}
 
-[testenv:venv-constraints]
-basepython = python3
-install_command = {[testenv:common-constraints]install_command}
-commands = {posargs}
-
 [testenv:cover]
 basepython = python3
 deps = {[testenv]deps}
@@ -46,37 +34,14 @@ commands =
     coverage html -d cover
     coverage xml -o cover/coverage.xml
 
-[testenv:cover-constraints]
-basepython = python3
-install_command = {[testenv:common-constraints]install_command}
-deps = {[testenv]deps}
-    coverage
-setenv =
-    PYTHON=coverage run --source oslo_upgradecheck --parallel-mode
-commands =
-    stestr run '{posargs}'
-    coverage combine
-    coverage html -d cover
-    coverage xml -o cover/coverage.xml
-
 [testenv:docs]
 basepython = python3
 commands = sphinx-build -W -b html doc/source doc/build/html
 
-[testenv:docs-constraints]
-basepython = python3
-install_command = {[testenv:common-constraints]install_command}
-commands = sphinx-build -W -b html doc/source doc/build/html
-
 [testenv:debug]
 basepython = python3
 commands = oslo_debug_helper {posargs}
 
-[testenv:debug-constraints]
-basepython = python3
-install_command = {[testenv:common-constraints]install_command}
-commands = oslo_debug_helper {posargs}
-
 [testenv:lower-constraints]
 deps =
   -c{toxinidir}/lower-constraints.txt