[IMP] mail: mail_thread: message routing: raise exceptions instead of using asserts.
Indeed assert are statements meant to be used when developping, for
debug purpose. In a production environment it is safer to use real
exceptions that can be managed accordingly.
[FIX] mail: fixed tests, no more assertionerror, but valueerror
[FORWARD] [FIX] Forward port of revision 6920 of 6.1 addons branch.
Revid: revid:odo@openerp.com-20120727150051-e1q0m92tyrazz82f
Purpose: some fixes and more robuts handling of incoming emails
[DOC] mail_thread: docstrings to add raised exceptions in message_process and message_route
[IMP] fetchmail: try / except the processinf of each email and log any exception
found during processing. This way, all emails in the queue are managed and
all failed emails have their own exception in the logs, allowing easier
debugging.
Note that a failed email is set as seen to avoid processing it every time
the scheduler runs.
[MERGE] Sync with upstream (7.0)
[FIX] fetchmail: typos in logger messages
[MERGE] [FIX] fetchmail: more coherent and robust behavior of fetchmail. Notably, do not discard the whole email stack or stop after first crashed email processing.

Featuring:
- [FORWARD] [FIX] Forward port of revision 6920 of 6.1 addons branch, revid:odo@openerp.com-20120727150051-e1q0m92tyrazz82f. Purpose: some fixes and more robuts handling of incoming emails
- [IMP] mail: mail_thread: message routing: raise exceptions instead of using asserts. Indeed assert are statements meant to be used when developping, for debug purpose. In a production environment it is safer to use real exceptions that can be managed accordingly.
- [FIX] mail: fixed tests, no more AssertionError, but ValueError
- [IMP] fetchmail: try / except each email processing. This allows to print an exception in the logs for every failed email processing, without crashing the whole stack. Any failed or succeeded email is set as seen, to avoid crashing every time the scheduler runs.