Issue2786

>>> 3L - None
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -: 'long' and 'NoneType'
>>> None - 3L
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: xxx
>>> None - 3.0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -: 'NoneType' and 'float'

These errors conform with CPython 2.7:

% python
Python 2.7.14 (default, Apr 25 2018, 15:22:05)
[GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 3L - None
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -: 'long' and 'NoneType'
>>> None - 3L
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -: 'NoneType' and 'long'
>>> None - 3.0
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -: 'NoneType' and 'float'

One minor: we should fix the specific error message for 

>>> None - 3L
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: xxx

That specific error message of xxx looks like a TODO.

Ooops, I was reading the report wrong, it's exactly about the xxx in the error message. Sorry about that!