Invalid E231 missing whitespace after ':' with Python 3.12

[grische]

Only the Python 3.12 run shows this specific error, while Python 3.10 and Python 3.11 succeed successfully:

flake8 . --count --show-source --statistics
./extremeflash/tftp_server.py:28:63: E231 missing whitespace after ':'
        logging.info(f"Starting tftp server on {self.listenip}:{self.port} from {self.tmpdir}")
                                                              ^
1     E231 missing whitespace after ':'
1

See https://github.com/grische/extremeflash/actions/runs/5586345253/jobs/10210258182?pr=3

The respective code can be found here:
https://github.com/grische/extremeflash/blob/b8419e6bc283cfcd3052f054961ba977d9d3aec4/extremeflash/tftp_server.py#L27-L32

[grische]

Fixed with #1148