There's a bit of history I don't understand and couldn't find the appropriate trail for.

The original error message from the 2.6 era:

$ python2.6 -c 0[0]
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: 'int' object is unsubscriptable


This was changed in https://github.com/python/cpython/commit/f5fd5239819c5dfb1d7a33484be49dc705544d02 for clarity

As seen in 2.7.1

$ ./python2.7.1 -c 0[0]
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: 'int' object is not subscriptable


It was later changed in the 2.7 era here: 
https://github.com/python/cpython/commit/7d1483cbadbe48620964348a2039690624e7dc8e


To this error message (as demonstrated with 2.7.12):

$ python2.7 -c 0[0]
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: 'int' object has no attribute '__getitem__'


However, this patch never made it into the 3.x branch:

$ python3.6 -c 0[0]
Traceback (most recent call last):
  File "<string>", line 1, in <module>
TypeError: 'int' object is not subscriptable


Should this patch be (have been) cherry picked into master?