Allow paunch to be called as a python module

Includes a test that we can succesfully call it as a module in order
to avoid regressions.

This is essential fix related to python3 work as the only way to
enforce a specific python interpreter to be used.

Change-Id: If5c4bda5ddc708bfb3701800cea46e89a026fb6e
Story: https://tree.taiga.io/project/tripleo-ci-board/task/361

setup.cfg

@@ -24,9 +24,9 @@ packages =
 
 [entry_points]
 console_scripts =
-    paunch = paunch.main:main
+    paunch = paunch.__main__:main
 
-paunch = 
+paunch =
     apply = paunch.cmd:Apply
     cleanup = paunch.cmd:Cleanup
     delete = paunch.cmd:Delete
@@ -59,3 +59,6 @@ output_file = paunch/locale/paunch.pot
 all_files = 1
 build-dir = releasenotes/build
 source-dir = releasenotes/source
+
+[wheel]
+universal = 1

tox.ini

@@ -1,14 +1,20 @@
 [tox]
 minversion = 2.0
 envlist = py35,py27,pep8
-skipsdist = True
- 
+skipsdist = False
+
 [testenv]
 setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
-commands = bash -c 'if [ ! -d ./.testrepository ] ; then testr init ; fi'
-           testr run {posargs}
+install_command = pip install -U {opts} {packages}
+whitelist_externals =
+    bash
+commands =
+    python -m paunch --version
+    paunch --version
+    bash -c 'if [ ! -d ./.testrepository ] ; then testr init ; fi'
+    testr run {posargs}
 
 [testenv:pep8]
 basepython = python3