[1.7.x] Fixed #20815 -- Don't enforce unbuffered I/O on Python 3.
[1.7.x] Fixed #20815 -- Don't enforce unbuffered I/O on Python 3.

No test because this code is already deprecated (part of FastCGI support).

Backport of 5836a577 from master

jyotsna1820/django,jyotsna1820/django,oscaro/django,oscaro/django,jyotsna1820/django,oscaro/django,oscaro/django,jyotsna1820/django