UnicodeDecodeError from tty.readline(), u-Blox 8

[Hal Murray]

Can somebody give me a lesson on this area?

The code is:
  tty = open("/dev/ttyACM0")
  forever:
    line = tty.readline()


a) How do I read mostly ASCII without crashing when there is non-ASCII?

b) Why is a u-Blox LEA-M8T sending me non-ASCII crap?
  This is coming from the USB port.  It's running in NMEA mode.
  I don't think I have sent it any commands.

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