Update validity check for experiment names to be case sensitive

The sixpack-py client allows for experiment names to be uppercased, but
the javascript and ruby clients enforce lowecase experiment names only.
This PR updates the client code to match the javascript and ruby
implementations.

+ Add another regex for experiment name and use that for validation
+ Add tests

sixpack/sixpack.py

@@ -4,6 +4,12 @@
 
 SIXPACK_HOST = 'http://localhost:5000'
 SIXPACK_TIMEOUT = 0.5
+
+# valid experiment_names must be lowercase, start with an alphanumeric and
+# contain alphanumerics, dashes and underscores
+VALID_EXPT_NAME_RE = re.compile(r"^[a-z0-9][a-z0-9\-_ ]*$")
+
+# Valid alternative and kpi names
 VALID_NAME_RE = re.compile(r"^[a-z0-9][a-z0-9\-_ ]*$", re.I)
 
 
@@ -42,7 +48,7 @@ def __init__(self, client_id=None, options=None, params=None):
             self.client_id = client_id
 
     def participate(self, experiment_name, alternatives, force=None, traffic_fraction=1, prefetch=False):
-        if VALID_NAME_RE.match(experiment_name) is None:
+        if VALID_EXPT_NAME_RE.match(experiment_name) is None:
             raise ValueError('Bad experiment name')
 
         if len(alternatives) < 2:
@@ -72,7 +78,7 @@ def participate(self, experiment_name, alternatives, force=None, traffic_fractio
         return response
 
     def convert(self, experiment_name, kpi=None):
-        if VALID_NAME_RE.match(experiment_name) is None:
+        if VALID_EXPT_NAME_RE.match(experiment_name) is None:
             raise ValueError('Bad experiment name')
 
         params = {

sixpack/test/test_sixpack_client.py

@@ -59,7 +59,7 @@ def test_client_id_on_constructor(self):
         session = sixpack.Session(client_id='zack111')
         self.assertEqual(session.client_id, 'zack111')
 
-    def test_failure_on_bad_experiment_name(self):
+    def test_failure_on_bad_experiment_name_participate(self):
         session = sixpack.Session('zack')
         with self.assertRaises(ValueError):
             session.participate('*********', ['1', '2'])
@@ -69,6 +69,16 @@ def test_failure_on_bad_exp_name_convert(self):
         with self.assertRaises(ValueError):
             session.convert('(((((')
 
+    def test_failure_on_uppercase_expt_name_participate(self):
+        session = sixpack.Session('zack')
+        with self.assertRaises(ValueError):
+            session.participate('FooExperiment', ['1', '2'])
+
+    def test_failure_on_uppercase_expt_name_convert(self):
+        session = sixpack.Session('zack')
+        with self.assertRaises(ValueError):
+            session.convert('FooExperiment')
+
     def test_failure_on_bad_kpi_name_convert(self):
         session = sixpack.Session('zack')
         with self.assertRaises(ValueError):