gh-102799: use sys.exception() instead of sys.exc_info() in pdb (#103294)

Lib/pdb.py

@@ -1258,7 +1258,7 @@ class Pdb(bdb.Bdb, cmd.Cmd):
             return _rstr('** raised %s **' % self._format_exc(exc))
 
     def _error_exc(self):
-        exc = sys.exc_info()[1]
+        exc = sys.exception()
         self.error(self._format_exc(exc))
 
     def _msg_val_func(self, arg, func):
@@ -1755,9 +1755,10 @@ def post_mortem(t=None):
     """
     # handling the default
     if t is None:
-        # sys.exc_info() returns (type, value, traceback) if an exception is
-        # being handled, otherwise it returns None
-        t = sys.exc_info()[2]
+        exc = sys.exception()
+        if exc is not None:
+            t = exc.__traceback__
+
     if t is None:
         raise ValueError("A valid traceback must be passed if no "
                          "exception is being handled")
@@ -1841,18 +1842,18 @@ def main():
         except Restart:
             print("Restarting", target, "with arguments:")
             print("\t" + " ".join(sys.argv[1:]))
-        except SystemExit:
+        except SystemExit as e:
             # In most cases SystemExit does not warrant a post-mortem session.
             print("The program exited via sys.exit(). Exit status:", end=' ')
-            print(sys.exc_info()[1])
+            print(e)
         except SyntaxError:
             traceback.print_exc()
             sys.exit(1)
-        except:
+        except BaseException as e:
             traceback.print_exc()
             print("Uncaught exception. Entering post mortem debugging")
             print("Running 'cont' or 'step' will restart the program")
-            t = sys.exc_info()[2]
+            t = e.__traceback__
             pdb.interaction(None, t)
             print("Post mortem debugger finished. The " + target +
                   " will be restarted")