Bug 1658679 - Fix Python 3 compatibility in RemoteAutomation.read_stdout(). r=jmaher

Differential Revision: https://phabricator.services.mozilla.com/D86958

build/mobile/remoteautomation.py

@@ -272,6 +272,7 @@ class RemoteAutomation(object):
             return False
         if not newLogContent:
             return False
+        newLogContent = six.ensure_str(newLogContent, errors='replace')
 
         self.stdoutlen += len(newLogContent)