SF bug #652933 (for IdleFork): Open Module "math" Fails

When a module doesn't have a __path__ attribute, trigger a dialog box
rather than dumping a traceback to the console.

Tools/idle/EditorWindow.py

@@ -91,7 +91,10 @@ def _find_module(fullname, path=None):
         if descr[2] == imp.PY_SOURCE:
             break                   # find but not load the source file
         module = imp.load_module(tgt, file, filename, descr)
-        path = module.__path__
+        try:
+            path = module.__path__
+        except AttributeError:
+            raise ImportError, 'No source for module ' + module.__name__
     return file, filename, descr
 
 class EditorWindow: