Fix TypeError: Object of type DBusException is not JSON serializable

When a datastore exception occurs, the error cannot be sent to the
caller because the object cannot be serialised.  Problem was inherent in
original design.

Convert the exception to a string before sending it.

Related to
#909

Part of
#911

Signed-off-by: James Cameron <[email protected]>

Author: shaansubbaiah

src/jarabe/apisocket.py

@@ -261,6 +261,9 @@ def send_result(self, request, result):
         self._session.send_message(json.dumps(response))
 
     def send_error(self, request, error):
+        if isinstance(error, dbus.exceptions.DBusException):
+            error = error.get_dbus_name() + " " + error.get_dbus_message()
+
         response = {"result": None,
                     "error": error,
                     "id": request["id"]}