Ignoring failed event notifications

These happen rarely and are not a big deal when they do. We still log them to
the Vim message area, but we don't annoy the user with the default, in-your-face
Python traceback.

python/ycm/client/event_notification.py

@@ -17,6 +17,8 @@
 # You should have received a copy of the GNU General Public License
 # along with YouCompleteMe.  If not, see <http://www.gnu.org/licenses/>.
 
+import traceback
+from ycm import vimsupport
 from ycm.client.base_request import BaseRequest, BuildRequestData
 
 
@@ -33,7 +35,15 @@ class EventNotification( BaseRequest ):
       request_data.update( self._extra_data )
     request_data[ 'event_name' ] = self._event_name
 
+    # On occasion, Vim tries to send event notifications to the server before
+    # it's up. This causes intrusive exception messages to interrupt the user.
+    # While we do want to log these exceptions just in case, we post them
+    # quietly to the Vim message log because nothing bad will happen if the
+    # server misses some events and we don't want to annoy the user.
+    try:
       self.PostDataToHandler( request_data, 'event_notification' )
+    except:
+      vimsupport.EchoText( traceback.format_exc() )
 
 
 def SendEventNotificationAsync( event_name, extra_data = None ):