Juan David González Cobas authored Dec 01, 2020 and Tomasz Wlostowski committed Dec 17, 2020

Two safety nets are added here:

  * PYTHON variable that can be set to the interpreter path (defaults to
    "python3"), so that the system default can be overriden
  * the PORT arg to usb-bootloader.py is passed as an empty string if
    unset, to produce an explicit error