Modified patch from upstream (PyColorize.py was moved):
commit 3323d576db9f982be1ef6d66f7b9e0d0d6fef7db
Author: Thomas Spura <tomspur@fedoraproject.org>
Date:   Tue Aug 31 14:12:37 2010 +0200

    pycolor: Wrong filename given -> print error
    
    When a user wanted to colorize a file, which doesn't exist, IPython
    would crash. This commit changes this, so the user gets a usefull
    message about the wrong filename.
    
    This fixes RH bug #628742.
    
    Signed-off-by: Thomas Spura <tomspur@fedoraproject.org>

diff --git a/IPython/utils/PyColorize.py b/IPython/utils/PyColorize.py
index 613ae19..1bd9919 100644
--- a/IPython/PyColorize.py
+++ b/IPython/PyColorize.py
@@ -277,7 +277,11 @@ If no filename is given, or if filename is -, read standard input."""
     if fname == '-':
         stream = sys.stdin
     else:
-        stream = file(fname)
+        try:
+            stream = file(fname)
+        except IOError,msg:
+            print msg
+            return
 
     parser = Parser()