Added doc-string comment regarding reason for patch, and details on try/catch change.

IPython/external/decorator/_decorator.py

@@ -30,6 +30,9 b''
 """
 Decorator module, see http://pypi.python.org/pypi/decorator
 for the documentation.
+
+NOTE: this is an IPython-patched version to work on IronPython. See
+      FIXED comment below.
 """
 from __future__ import print_function
 
@@ -139,6 +142,8 b' class FunctionMaker(object):'
         func.__defaults__ = getattr(self, 'defaults', ())
         func.__kwdefaults__ = getattr(self, 'kwonlydefaults', None)
         func.__annotations__ = getattr(self, 'annotations', None)
+        # FIXED: The following is try/execpted in IPython to work 
+        # with IronPython.
         try:
             callermodule = sys._getframe(3).f_globals.get('__name__', '?')
         except AttributeError: # IronPython _getframe only exists with FullFrames