BF: iohub eyelink sendMessage saving byte array

In Python3 sendMessage() method of the iohub eyelink eyetracker class was sending byte arrays to pylink sendMessage() instead of String, resulting in b'....' being added to message contents in EDF file.  Now byte arrays are converted to a string using 'utf-8'.

psychopy/iohub/devices/eyetracker/hw/sr_research/eyelink/eyetracker.py

@@ -371,18 +371,22 @@ def sendMessage(self, message_contents, time_offset=None):
 
         """
         try:
+            if isinstance(message_contents, bytes):
+                message_contents = message_contents.decode('utf-8')
+
             if time_offset:
                 r = self._eyelink.sendMessage(
                     '\t%d\t%s' %
                     (time_offset, message_contents))
             else:
-                r = self._eyelink.sendMessage(message_contents)
+                r = self._eyelink.sendMessage('%s'%message_contents)
 
             if r == 0:
                 return EyeTrackerConstants.EYETRACKER_OK
             return EyeTrackerConstants.EYETRACKER_ERROR
         except Exception as e:
             printExceptionDetailsToStdErr()
+        return EyeTrackerConstants.EYETRACKER_ERROR
 
     def runSetupProcedure(self):
         """Start the EyeLink Camera Setup and Calibration procedure.