'Signal that a new file has been started.
Warning: As with any data from the client, you should not trust
content_length (and sometimes won\'t even get it).'

def new_file(self, field_name, file_name, content_type, content_length, charset=None):

    self.field_name = field_name
    self.file_name = file_name
    self.content_type = content_type
    self.content_length = content_length
    self.charset = charset
