return statements should comply with PEP 8

[eenblam]

https://www.python.org/dev/peps/pep-0008/

e.g. in peekapp/peekapp/blacklist.py, Blacklist.filter_by_URL has three different return formats.

    def filter_by_URL(self, pkt):
        # Assume unencrypted HTTP packet
        try:
            raw_load = pkt.payload.load
        except AttributeError:
            return

        first = raw_load.split('\r\n')[0].strip()

        try:
            # RFC2616
            # https://www.w3.org/Protocols/rfc2616/rfc2616-sec5.html#sec5
            method, identifier, version = first.split()
        except ValueError:
            # Wrong number of values to unpack; mal-formed HTTP at best
            return

        if method in ['GET', 'HEAD', 'POST', 'PUT',
                'OPTIONS', 'DELETE', 'TRACE', 'CONNECT']:
            for rule in self.URLs:
                if rule in identifier:
                    return classify_pkt(pkt, 'ILLEGAL_URL',
                            payload=identifier, rule=rule)
        return None

return
return classify_pkt(...)
return None