'`ext=class\' where `class\' is added as a Processor for files ending
with `ext\'.'

def opt_processor(self, proc):

    if (not isinstance(self['root'], static.File)):
        raise usage.UsageError('You    can    only    use    --processor    after    --path.')
    (ext, klass) = proc.split('=', 1)
    self['root'].processors[ext] = reflect.namedClass(klass)
