tox: Configure 'ignore_basepython_conflict'

Resolves the following warning:

  UserWarning: conflicting basepython version (set 37, should be 36) for
  env 'py36';resolve conflict or set ignore_basepython_conflict

and makes sure we're testing with what we should be.

Some random indentation is fixed while we're here.

Change-Id: I6f3e98cc33731f528a3a755300f1fcc65c6b53ff
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>

tox.ini

@@ -1,19 +1,20 @@
 [tox]
 envlist = py37,pep8,docs
-minversion = 2.0
-skipsdist = True
+minversion = 3.1
+skipsdist = true
+ignore_basepython_conflict = true
 
 [testenv]
 basepython = python3
-usedevelop = True
+usedevelop = true
 # tox is silly... these need to be separated by a newline....
 whitelist_externals =
   find
   rm
   make
-passenv = ZUUL_CACHE_DIR
-          REQUIREMENTS_PIP_LOCATION
-install_command = pip install {opts} {packages}
+passenv =
+  ZUUL_CACHE_DIR
+  REQUIREMENTS_PIP_LOCATION
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/test-requirements.txt
@@ -71,13 +72,13 @@ commands =
 
 [testenv:cover]
 setenv =
-    PYTHON=coverage run --source novaclient --parallel-mode
+  PYTHON=coverage run --source novaclient --parallel-mode
 commands =
-    stestr run {posargs}
-    coverage combine
-    coverage html -d cover
-    coverage xml -o cover/coverage.xml
-    coverage report
+  stestr run {posargs}
+  coverage combine
+  coverage html -d cover
+  coverage xml -o cover/coverage.xml
+  coverage report
 
 [flake8]
 # Following checks should be enabled in the future.
@@ -89,7 +90,7 @@ commands =
 #
 # Additional checks are also ignored on purpose: F811, F821
 ignore = E731,F811,F821,H404,H405
-show-source = True
+show-source = true
 exclude=.venv,.git,.tox,dist,*lib/python*,*egg,build,doc/source/conf.py,releasenotes
 
 [hacking]