'import foo as _foo' is useful in exported modules to avoid 'foo' being
present in the public API. No need to play that game in test code.

This is a lazy workaround: 4c9a241949067fc8d55f3ea12170ad364bd8b18d
is amended to do nothing on python2, so we have the same issue that
was present before. This allows the code to execute, and hopefully
almost nobody is using python2 code anyway.

f868a56b935b6152d611b22f7a5538f14dafb194 is amended in the same way.
For python2 code we have the same lack of timezone-awareness as before.

This allows the tests to pass under python 2.7.

This change enables to add extra fields to JournalHandler in a
configuration file loaded by `logging.config.fileConfig`, which only allows positional
parameters:

class=systemd.journal.JournalHandler
args={'level': INFO, 'SYSLOG_IDENTIFIER': 'my-cool-app'}

[zj: originally the patch added a new positional parameter to
__init__(), but that is not backwards compatible. So I added a new
classmethod to allow the positional parameters to be passed.]

send() already does conversions in a type-specific way, and doing it
in journal handler would defeat those conversions. In particular, UUIDs
would be converted to early and have dashes.

MESSAGE_ID passing was broken before previous commit:
TypeError: send() got multiple values for keyword argument 'MESSAGE_ID'

With the previous commit it's broken differently:

______________________________ test_journalhandler_message_id_on_handler _______________________________

    def test_journalhandler_message_id_on_handler():
        record = logging.LogRecord('test-logger', logging.INFO, 'testpath', 1, 'test', None, None)
        sender = MockSender()
        handler = journal.JournalHandler(logging.INFO, sender_function=sender.send,
                                         MESSAGE_ID=TEST_MID)
        handler.emit(record)
        assert len(sender.buf) == 1
>       assert 'MESSAGE_ID=' + TEST_MID.hex in sender.buf[0]
E       assert ('MESSAGE_ID=' + '8441372f8dca4ca98694a6091fd8519f') in ['MESSAGE=test', 'MESSAGE_ID=8441372f-8dca-4ca9-8694-a6091fd8519f', 'CODE_FILE=testpath', 'CODE_LINE=1', 'name=test-logger', 'exc_info=None', ...]
E        +  where '8441372f8dca4ca98694a6091fd8519f' = UUID('8441372f-8dca-4ca9-8694-a6091fd8519f').hex

systemd/test/test_journal.py:116: AssertionError
______________________________ test_journalhandler_message_id_on_message _______________________________

    def test_journalhandler_message_id_on_message():
        record = logging.LogRecord('test-logger', logging.INFO, 'testpath', 1, 'test', None, None)
        record.__dict__['MESSAGE_ID'] = TEST_MID2
        sender = MockSender()
        handler = journal.JournalHandler(logging.INFO, sender_function=sender.send,
                                         MESSAGE_ID=TEST_MID)
        handler.emit(record)
        assert len(sender.buf) == 1
>       assert 'MESSAGE_ID=' + TEST_MID2.hex in sender.buf[0]
E       assert ('MESSAGE_ID=' + '8441370000000000000000001fd85000') in ['MESSAGE=test', 'MESSAGE_ID=84413700-0000-0000-0000-00001fd85000', 'CODE_FILE=testpath', 'CODE_LINE=1', 'name=test-logger', 'exc_info=None', ...]
E        +  where '8441370000000000000000001fd85000' = UUID('84413700-0000-0000-0000-00001fd85000').hex

systemd/test/test_journal.py:135: AssertionError
============================ 2 failed, 53 passed, 6 skipped in 0.16 seconds ============================

Let's not try to make it look like a journal field. It should
be a normal parameter.

Followup for dce0a855c3281e7051b1cbe0f73386d1c90ef320.

Backwards compatibility for mapPriority is retained.

daemon: add basic support for sd_is_socket_sockaddr