[docs] Doc: remove errors about mixed-type comparisons. (issue 12067)

[blckknght at gmail.com]

I think the patch is great, with the exception of one line (which I have
several issues with).


http://bugs.python.org/review/12067/diff/12409/Doc/reference/expressions.rst
File Doc/reference/expressions.rst (right):

http://bugs.python.org/review/12067/diff/12409/Doc/reference/expressions.rst#newcode1120
Doc/reference/expressions.rst:1120: Strings cannot directly be compared
with binary sequences, and vice versa!
I think the "be" is misplaced in this sentence (it should be "cannot be
directly compared").

Further, the "and" conjunction seemed so jarring to me I wasn't sure it
was even grammatical (though after further consideration I understand it
now). I'd suggest dropping the whole "vice versa" clause, since the
ability to be compared is symmetric (even if the comparisons themselves
are not). It wouldn't make sense to say that A can be compared to B if B
cannot be compared to A.

And finally, the exclamation mark at the end is a bit overemphatic!!1!

tldr, make this sentence: "Strings and binary sequences cannot be
directly compared."

http://bugs.python.org/review/12067/