On exception, the traceback is concatenated to the message

[sergeykad]

In the case of execution of logger.exception("Oops") reading Record.msg in a custom logging.Handler implementation returns the original message with traceback concatenated to it. Since I need to use a different format for different handlers this is quite problematic. This is also different from Python logging, which stores traceback in Record.exc_text and concatenates it later with the formatted message.

This is somewhat related to #1080

[Delgan]

This is because {exception} is automatically appended to your format for convenience. This behavior is disabled when using a function as the formatter.

logger.add(custom_handler, format=lambda _: "{message}")