Improve logging of GithubTriggerEvents

The GithubTriggerEvents currently don't log any detail of the event
itself. This makes it hard to analize issues using the log. We should
add more details about the action, project and pull request if
available.

Change-Id: Id07aa2c0bcfe743a0bfa34d635e77e9ecac4dc48

zuul/driver/github/githubmodel.py

@@ -53,6 +53,7 @@ class GithubTriggerEvent(TriggerEvent):
         self.title = None
         self.label = None
         self.unlabel = None
+        self.action = None
         self.delivery = None
 
     def isPatchsetCreated(self):
@@ -67,6 +68,11 @@ class GithubTriggerEvent(TriggerEvent):
 
     def _repr(self):
         r = [super(GithubTriggerEvent, self)._repr()]
+        if self.action:
+            r.append(self.action)
+        r.append(self.canonical_project_name)
+        if self.change_number:
+            r.append('%s,%s' % (self.change_number, self.patch_number))
         if self.delivery:
             r.append('delivery: %s' % self.delivery)
         return ' '.join(r)