change wording of exception

Author: Carreau

Lib/pdb.py

@@ -492,9 +492,7 @@ def interaction(self, frame, tb_or_exc):
 
         _chained_exceptions, tb = self._get_tb_and_exceptions(tb_or_exc)
         if not _chained_exceptions and isinstance(tb_or_exc, BaseException):
-            raise ValueError(
-                "A valid traceback must be passed if no exception is being handled"
-            )
+            raise ValueError("No exception traceback to inspect")
         with self._hold_exceptions(_chained_exceptions):
             if self.setup(frame, tb):
                 # no interaction desired at this time (happens if .pdbrc contains

Lib/test/test_pdb.py

@@ -1132,7 +1132,7 @@ def test_post_mortem_single_no_stack():
     ...        test_function()
     ...    except ValueError as e:
     ...        print(e)
-    A valid traceback must be passed if no exception is being handled
+    No exception traceback to inspect
     """