encoding str works in both Cpython and circuitpython. fixed echotest

Author: ladyada

adafruit_gps.py

@@ -125,7 +125,7 @@ def send_command(self, command, add_checksum=True):
             for char in command:
                 checksum ^= char
             self._uart.write(b'*')
-            self._uart.write('{:02x}'.format(checksum).upper().encode())
+            self._uart.write(bytes('{:02x}'.format(checksum).upper(),"utf-8"))
         self._uart.write(b'\r\n')
 
     @property

examples/gps_echotest.py

@@ -11,8 +11,8 @@
 # Define RX and TX pins for the board's serial port connected to the GPS.
 # These are the defaults you should use for the GPS FeatherWing.
 # For other boards set RX = GPS module TX, and TX = GPS module RX pins.
-#RX = board.RX
-#TX = board.TX
+RX = board.RX
+TX = board.TX
 
 # Create a serial connection for the GPS connection using default speed and
 # a slightly higher timeout (GPS modules typically update once a second).