Adding unittests (#300)

* Create a custom class to handle aborting 204 properly.  If this isn't
covered the server will send a 500 due to a python exception

* Moved py.test configuration under tool:pytest, this was causing a
warning.  This is new to 3.0.1 which is now the pinned version

* Unittest for puppetboard.utils

puppetboard/app.py

@@ -25,6 +25,8 @@ from puppetboard.utils import (
     jsonprint, prettyprint, Pagination
 )
 
+import werkzeug.exceptions as ex
+
 DEFAULT_ORDER_BY = '[{"field": "start_time", "order": "desc"}]'
 
 app = Flask(__name__)
@@ -93,6 +95,22 @@ def utility_processor():
     return dict(now=now)
 
 
+#
+# 204 doesn't have a mapping in werkzeug, we need to define a custom
+# class and then set it to the mappings.
+#
+class NoContent(ex.HTTPException):
+    code = 204
+    description = '<p>No content</p'
+
+abort.mapping[204] = NoContent
+
+
+@app.errorhandler(204)
+def no_content(e):
+    return '', 204
+
+
 @app.errorhandler(400)
 def bad_request(e):
     envs = environments()