How do I get logger to delete existing log file before writing to it again?

Try this:

filehandler_dbg = logging.FileHandler(
   logger.name + '-debug.log', 
   mode='w')

to open the filename in write mode instead of append mode, clobbering logger.name

More information: logging.FileHandler docs, open() and list of modes

If you are using any external configuration file then pass 'w' for write mode in args of the handler.

[loggers]
keys=root

[logger_root]
level=DEBUG
handlers=file_handler

[handlers]
keys=file_handler

[handler_file_handler]
class=FileHandler
formatter=formatter
args=("../log/test" + time.strftime("%%Y%%m%%d%%H%%M%%S") + '.log', 'w')

[formatters]
keys=formatter

[formatter_formatter]
format=%(asctime)s %(levelname)-5s [%(module)s] %(message)s