Fixed issue with universal_newlines and Python 3.7+
fixed issue with universal_newlines and Python 3.7 non-blocking IO with universal_newlines causes a can't concat NoneType to bytes issue, modified code to use byte strings instead
fixed issue with universal_newlines and Python 3.7 non-blocking IO with universal_newlines causes a can't concat NoneType to bytes issue, modified code to use byte strings instead