Fix mailgw IMAP message handling

Author: schlatterbeck

CHANGES.txt

@@ -184,6 +184,8 @@ Fixed:
 - issue2551013: Reversed sorting in hyperdb property wrapper object's
   sorted() method. Patch by David Sowder, application and doc change
   by John Rouillard.
+- issue2551066: IMAP mail handling wasn't working and produced a
+  traceback.
 
 2018-07-13 1.6.0
 

roundup/mailgw.py

@@ -1357,9 +1357,9 @@ def do_imap(self, server, user='', password='', mailbox='', ssl=0,
                 # mark the message as deleted.
                 server.store(str(i), '+FLAGS', r'(\Deleted)')
 
-                # process the message
-                s = io.BytesIO(data[0][1])
-                s.seek(0)
+                # process the message, data[0][1] is of type 'bytes' for
+                # python3 and a string for python2.
+                s = data[0][1]
                 self.handle_Message(message_from_bytes(s, RoundupMessage))
             server.close()
         finally: