[obv] printing.py: Add missing entry for RuntimeError to doc string.

[Doug Evans]

Hi.

fyi,
I'm checking this in as obvious.

2011-05-23  Doug Evans  <dje@google.com>

	* python/lib/gdb/printing.py (register_pretty_printer): Add missing
	entry for RuntimeError to doc string.

Index: python/lib/gdb/printing.py
===================================================================
RCS file: /cvs/src/src/gdb/python/lib/gdb/printing.py,v
retrieving revision 1.3
diff -u -p -r1.3 printing.py
--- python/lib/gdb/printing.py	1 Jan 2011 15:33:26 -0000	1.3
+++ python/lib/gdb/printing.py	23 May 2011 17:36:23 -0000
@@ -86,6 +86,7 @@ def register_pretty_printer(obj, printer
     Raises:
         TypeError: A problem with the type of the printer.
         ValueError: The printer's name contains a semicolon ";".
+        RuntimeError: A printer with the same name is already registered.
 
     If the caller wants the printer to be listable and disableable, it must
     follow the PrettyPrinter API.  This applies to the old way (functions) too.