Python runtime: bytes comprehension
I am too busy with other work so I am leaving this work item. I am implementing ProcessXor in Construct and found that this code
```py
        if PY2:
            return bytes(bytearray(v ^ key for v in bytearray(data)))
        else:
            return bytes(v ^ key for v in data)
```
could easily be
```py
            return bytes(v ^ key for v in data)
```
because bytes([1,2,3]) works on Python 2 as well.
