Might be worth making this addition from 3 (I'm not sure how to add this to 2)
-b     : issue warnings about str(bytes_instance), str(bytearray_instance)
         and comparing bytes/bytearray with str. (-bb: issue errors)


Building on Martin's example:

On all of these, python2 is
Python 2.7.6 (default, Apr  6 2014, 23:14:26)
[GCC 4.2.1 Compatible Apple LLVM 5.1 (clang-503.0.38)] on darwin
Type "help", "copyright", "credits" or "license" for more information.


emily-mba:cpython emily$ python2
>>> bytearray("3") == u"3"
False

emily-mba:cpython emily$ python2 -b
>>> bytearray("3") == u"3"
__main__:1: BytesWarning: Comparison between bytearray and string
False

emily-mba:cpython emily$ python2 -bb
>>> bytearray("3") == u"3"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
BytesWarning: Comparison between bytearray and string