fixup syntax error in python2 after 2to3 migration

fixup for 7d74c2e

there is one use of `print(str, file=...)` after the transition.

Author: v4hn

pr2_computer_monitor/scripts/cpu_monitor.py

@@ -34,7 +34,7 @@
 
 ##\author Kevin Watts
 
-from __future__ import with_statement
+from __future__ import with_statement, print_function
 import roslib
 roslib.load_manifest('pr2_computer_monitor')