mailbot: support MlEmail sorting

Every now and then some bot blasts a lot of emails at once
and we end up with the same exact dates in the defer queue.
The defer queue has tuples of data and MlEmail so when dates
are the same it tries to compare email instances. We don't
care which one gets to the start of the queue first, but
let's not crash.

Signed-off-by: Jakub Kicinski <[email protected]>

mailbot.py

@@ -262,6 +262,15 @@ def __init__(self, msg_path):
         self._series_author = None
         self._authorized = None
 
+    def __eq__(self, other):
+        return True
+
+    def __lt__(self, other):
+        return False
+
+    def __gt__(self, other):
+        return False
+
     def get(self, item, failobj=None):
         return self.msg.get(item, failobj)