Add basic tox targets for pep8 and build test

.gitignore

@@ -1 +1,2 @@
 .tox
+build

layer.yaml

@@ -1 +1,2 @@
 includes: ['layer:openstack']
+repo: 'https://github.com/openstack/charm-layer-openstack-principle'

requirements.txt

@@ -0,0 +1,5 @@
+# Requirements to build the layer
+charm-tools
+ruamel.yaml==0.10.12
+simplejson
+flake8

tox.ini

@@ -0,0 +1,26 @@
+[tox]
+skipsdist = True
+envlist = pep8,build
+
+[testenv]
+basepython = python2.7
+setenv = VIRTUAL_ENV={envdir}
+         PYTHONHASHSEED=0
+         TERM=linux
+         JUJU_REPOSITORY={toxinidir}/build
+passenv = http_proxy https_proxy
+install_command =
+  pip install {opts} {packages}
+deps =
+  -r{toxinidir}/requirements.txt
+whitelist_externals = /bin/true
+
+[testenv:build]
+commands =
+  charm-build --log-level DEBUG -o {toxinidir}/build .
+
+[testenv:venv]
+commands = {posargs}
+
+[testenv:pep8]
+commands = /bin/true