Fix import log_handler error with publish_errors set

Sync latest module log_handler from Oslo.
Commit Id is 2843a92a0e4007f50d5ad63d51fe574e1ba5e280

This handler sends the error to configured notifier.
The notifier could be any kind (log, RPC, no_op, None).

Note: when using publish_errors you also need to set the
notification_driver option too.

Closes-bug: #1240349
Change-Id: I4f759b049b8f34904ba11382a2e8fc1578677a8f
Merge "Fix import log_handler error with publish_errors set"