This commit fixes the following warning:
DeprecationWarning: 'U' mode is deprecated
Removing 'U' has no effect with Python 3 [1]:
There is an additional mode character permitted, 'U', which no
longer has any effect, and is considered deprecated. It previously
enabled universal newlines in text mode, which became the default
behaviour in Python 3.0.
[1] https://docs.python.org/3/library/functions.html?highlight=open#open
(cherry picked from commit 9715d3504c)
'cat.py' created by Richard Heck
This script resembles the unix command 'cat', valid now on every
platform.
git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@34828 a592a061-630c-0410-9148-cb99ea01b6c8