Merge "github: prevent AttributeError when missing branch protection"

tests/fakegithub.py

@@ -195,6 +195,10 @@ class FakeRepository(object):
 
     def get_url_protection(self, branch):
         contexts = self.data.required_contexts.get((self.name, branch), [])
+        if not contexts:
+            # Note that GitHub returns 404 if branch protection is off so do
+            # the same here as well
+            return FakeResponse({}, 404)
         data = {
             'required_status_checks': {
                 'contexts': contexts

zuul/driver/github/githubconnection.py

@@ -1116,7 +1116,7 @@ class GithubConnection(BaseConnection):
         resp = github.session.get(url, headers=headers)
 
         if resp.status_code == 404:
-            return None
+            return {}
 
         return resp.json()