File "/usr/lib64/python3.4/codecs.py", line 490, in read
    data = self.bytebuffer + newdata
TypeError: can't concat bytes to NoneType


            if size < 0:
                newdata = self.stream.read()
            else:
                newdata = self.stream.read(size)
            # decode bytes (those remaining from the last call included)
            data = self.bytebuffer + newdata

if self.stream is nonblocking, it's read will return None (py3, py2 raises IOError(EGAIN)).

Simple `if newdata is None: return None` should fix that I guess