[why]
Usually the variable `logger` holds the logger object and all logging
calls got through that.

But because we use the font filename as loggername that logger object
can only be set up after the arguments have been parsed. If some
messages are to be logged before the call needs to go to the root logger
called as `logging` class.

This means one needs to take `logger` or `logging` based on the time
when someting is to be logged. That can be confusing and is easily
wrong, especially if code is shifted.

[how]
Always use the `logger` variable and just let that point to the root
logger until we set up a concrete logger.

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>