--> from collections import deque
--> d = deque()
--> d += 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable

deque should be returning NotImplemented, which would generate a more appropriate error message:

TypeError: unsupported operand type(s) for -=: 'collections.deque' and 'int'

which is what happens with -=, *=, /=, |=, at which point I stopped testing.