Otherwise it breaks with str on py3:

	In [1]: from io import BytesIO

	In [2]: BytesIO("abc")
	---------------------------------------------------------------------------
	TypeError                                 Traceback (most recent call last)
	<ipython-input-2-52a130edd46d> in <module>()
	----> 1 BytesIO("abc")

	TypeError: a bytes-like object is required, not 'str'