Add gate jobs

Set ``toxworkdir`` to avoud charm-tools build recursion.

Change-Id: Ia9ed0f5e8e17d9d0ffdf3e650c76f2c36938244d

.gitreview

@@ -0,0 +1,4 @@
+[gerrit]
+host=review.openstack.org
+port=29418
+project=openstack/charm-layer-ceph.git

.travis.yml

@@ -1,9 +0,0 @@
-language: python
-python:
- - "3.6"
-install: pip install tox-travis charm-tools
-env:
-  - ENV=pep8
-  - ENV=build
-script:
-  - tox -e $ENV --workdir /tmp/tox

.zuul.yaml

@@ -0,0 +1,3 @@
+- project:
+    templates:
+      - python-charm-layer-jobs

tox.ini

@@ -1,9 +1,10 @@
 [tox]
 skipsdist = True
 envlist = pep8
+toxworkdir = /tmp/tox
 
 [testenv]
-basepython = python2.7
+basepython = python3
 setenv = VIRTUAL_ENV={envdir}
          PYTHONHASHSEED=0
          TERM=linux
@@ -18,37 +19,13 @@ whitelist_externals = /bin/true /bin/echo /bin/mkdir
 [testenv:build]
 commands =
   /bin/echo 'WARNING: *build* target is for testing only.'
-  mkdir -p {envdir}/tmp
+  /bin/mkdir -p {envdir}/tmp
   charm-build --log-level DEBUG -o {envdir}/tmp/build .
 
 [testenv:venv]
 basepython = python3
 commands = {posargs}
 
-[testenv:py27]
-basepython = python2.7
-deps = -r{toxinidir}/test-requirements.txt
-# TODO: Need to write unit tests then remove the following command.
-commands = /bin/true
-
-[testenv:py34]
-basepython = python3.4
-deps = -r{toxinidir}/test-requirements.txt
-# TODO: Need to write unit tests then remove the following command.
-commands = /bin/true
-
-[testenv:py35]
-basepython = python3.5
-deps = -r{toxinidir}/test-requirements.txt
-# TODO: Need to write unit tests then remove the following command.
-commands = /bin/true
-
-[testenv:py36]
-basepython = python3.6
-deps = -r{toxinidir}/test-requirements.txt
-# TODO: Need to write unit tests then remove the following command.
-commands = /bin/true
-
 [testenv:pep8]
 basepython = python3
 commands = flake8 --ignore=E402 actions/ reactive/