This is for exceptions that are inherently based on user errors and not
permission based. e.g. passing incorrect number of arguments, too many
arguments, or an invalid argument. CommandNotFound is not classified
under this since it isn't inherently a user input error in all cases.
Some invalid commands can simply be due to an odd bot prefix. It would
also diminish the usefulness of the new parent class if CommandNotFound
was included.
This allows you to strictly require a number of arguments. The default
behaviour in this case is still `True`, since it would be a breaking
change otherwise and is a sane default. However if someone would want
to set this to `False`, they would receive an exception of type
`TooManyArguments` if too many arguments are passed to a command.
Hopefully this removes the uses of `ctx.message.content == 'stuff'`
inside commands.
This change should make it a bit more intuitive to get the original
exception without having the gotcha of checking ``isinstance`` inside
the error handler.
