logging formatting styles cleanup

[jordens]

The logging message formatting is a inconsistent. Let's do the following:

• style="{" should be added to https://github.com/m-labs/artiq/blob/master/artiq/tools.py#L61
• https://github.com/m-labs/artiq/blob/master/artiq/coredevice/comm_serial.py should be cleaned up to use logger.level("format {}", *arguments) instead of logger.level("format {}".format(*arguments)). The latter is always evaluated which the former is evaluated only on message emission.
• all the other uses of logging should be switch from % to {} formatting.

[sbourdeauducq]

Did you get style="{" to work? I didn't. I also worry it may break compatibility with external modules (e.g. asyncio) that use old-style formatting.

[sbourdeauducq]

This does not work:

import logging

logger = logging.getLogger('simple_example')
ch = logging.StreamHandler()
formatter = logging.Formatter(style="{")
ch.setFormatter(formatter)
logger.addHandler(ch)

logger.warn('warn message {0}', 42)

[jordens]

Ack. Looks broken. Then let's keep the "%" formatting for logging which then only requires changing comm_serial.py to use lazy formatting.