The backport wasn't as straightforward as I'd hoped, and we've pretty much run out of time for 2.7.

One issue is that long.from_bytes(b, ...) converts b to bytes type using the equivalent of "bytes(b)".  This doesn't work well in 2.7 (consider "bytes([255, 0, 0])" for example.  So different code is needed in 2.7 when interpreting an arbitrary Python object as a sequence of bytes.

Perhaps the 2.7 version could just iterate over the given object, and raise an exception if any of the iterates are not integers in the range [0, 256).