Basically, a lot of the checks revolving "if x in y" could be written
more efficiently by doing the task anyway and ignoring the exception
a la the EAFP guideline.
Apparently the clever hack for logging in on_error was not so clever
after all. If logging isn't configured, by the logging modules
definition of not configured, which is root logger not having an
Handlers attached, it will call logging.basicConfig(). Which messes up
setups that define handlers for other loggers than the root logger.
Going directly to the root logger rather than using the broken
convenience methods for logger is not an option either, as logger before
Python 3.2 does not have lastResort on the root logger, and prints an
error when invoked without any handlers.
Resolve by printing tracebacks to stderr by default in on_error.
Change the default implementation of on_error to log to the root logger
instead of discord.client and clarify that the exception is being
ignored. This ensures that a message will be output to standard error
in case the logging module has not been configured.
Also removes the argument printing for the default on_error, this is due
to them often being too long, that they could cause another exception to
be thrown, and because it sometimes causes sensitive information to be
output such as Discord tokens and session ids. It was also possible for
the length to get in the megabyte range with exceptions thrown by
on_socket_raw_receive in READY events.
Rapptz
Khazhismel
Red_M
Hornwitser