The previous implementation (result of #155) of disabling the
unused-argument warning for functions/methods having an argument named
`request` was to broad. As soon as a function/method contains a
`request` argument no unused-argument warning will be issued for this
function anymore, even though some other arguments are unused!

This commit monkey patches `VariablesChecker._is_ignored_named` to
specifically suppress the generation of unused-argument warnings for
arguments named `request`.
This way unused-argument warnings will still be issued for every other
unused argument of the function/method.