idf.py: Fix encoding issue with serial port names on Windows

Closes https://github.com/espressif/esp-idf/issues/3334

tools/idf.py

@@ -507,7 +507,7 @@ def get_default_serial_port():
     ports = list(reversed(sorted(
         p.device for p in serial.tools.list_ports.comports())))
     try:
-        print("Choosing default port %s (use '-p PORT' option to set a specific serial port)" % ports[0])
+        print("Choosing default port %s (use '-p PORT' option to set a specific serial port)" % ports[0].encode('ascii', 'ignore'))
         return ports[0]
     except IndexError:
         raise RuntimeError("No serial ports found. Connect a device, or use '-p PORT' option to set a specific port.")