[hooks] don't crash in start_period_tests if we can't find a branch head
If branch_head(branch) returns None, just ignore it instead of crashing.
--- a/hooks.py Tue Apr 22 12:14:58 2014 +0200
+++ b/hooks.py Fri Jan 24 11:39:31 2014 +0100
@@ -48,6 +48,8 @@
continue
heads = (head,)
for head in heads:
+ if head is None:
+ continue
# only start test if the config hasn't been executed against
# current branch head
if session.execute(