Originally posted by Russell Keith-Magee on Twitter:
https://twitter.com/freakboy3742/status/812609675283681280

Reproduced successfully on Python 3.5.2

>>> x = bytearray(1)
>>> y = {}
>>> x % y
Python3.5: bytearray(b'')
Python3.6: bytearray(b'\x00')

also:
>>> bytearray([0,1]) % {} # same with [], (), range(42)
bytearray(b'')
>>> bytearray([1,0]) % {}
bytearray(b'\x01')