De-duplicate the error log/notification system

Duplicate error messages (error.log entries, email notifications) aren't helpful and can make the situation worse.

assigned to @rswindell

mentioned in issue #834 (closed)

Received over 500 emails over night with duplicate alerts. Would appreciate a fix, thank you.

mentioned in commit 5f89c517

mentioned in commit 203d4151

mentioned in commit 169b770f

mentioned in commit ce7d83ee

mentioned in commit d8cfb579

Much progress has been made on this, but now it's more of a whack-a-mole situation. If you see more dupes (consecutive repeated error messages), let me know.

closed