Fixed #18013 -- Use the new 'as' syntax for exceptions.

Thanks Clueless for the initial patch.
Note that unittest has been purposely left out (external package only used by Python 2.6).

django/dispatch/dispatcher.py

@@ -205,7 +205,7 @@ class Signal(object):
         for receiver in self._live_receivers(_make_id(sender)):
             try:
                 response = receiver(signal=self, sender=sender, **named)
-            except Exception, err:
+            except Exception as err:
                 responses.append((receiver, err))
             else:
                 responses.append((receiver, response))

django/dispatch/saferef.py

@@ -119,10 +119,10 @@ class BoundMethodWeakref(object):
                 try:
                     if callable( function ):
                         function( self )
-                except Exception, e:
+                except Exception as e:
                     try:
                         traceback.print_exc()
-                    except AttributeError, err:
+                    except AttributeError as err:
                         print '''Exception during saferef %s cleanup function %s: %s'''%(
                             self, function, e
                         )