nicer crash on %rep if not in history'

IPython/history.py

@@ -173,9 +173,13 def rep_f(self, arg):
                 return
         
 
+    try:
     lines = self.extract_input_slices(args, True)
     print "lines",lines
     ip.runlines(lines)
+    except ValueError:
+        print "Not found in recent history:", args
+        
 
 
 _sentinel = object()