set_trace fails with IndexError

[alanbernstein]

The below stack trace occurs when I call set_trace(). The program otherwise runs without error with that set_trace removed. pdb.set_trace() does not have the same problem. I am working on finding a minimal producer, but I hoped I could get a clue before sinking too much time into that.

Traceback (most recent call last):
  File "search_tools/smart_search.py", line 260, in <module>
    main(sys.argv)
  File "search_tools/smart_search.py", line 64, in main
    run_commands(cmds, verbosity)
  File "search_tools/smart_search.py", line 81, in run_commands
    set_trace()
  File "/home/alan/.local/lib/python3.8/site-packages/ipdb/__main__.py", line 77, in set_trace
    p = _init_pdb(context).set_trace(frame)
  File "/home/alan/.local/lib/python3.8/site-packages/ipdb/__main__.py", line 54, in _init_pdb
    debugger_cls = _get_debugger_cls()
  File "/home/alan/.local/lib/python3.8/site-packages/ipdb/__main__.py", line 34, in _get_debugger_cls
    ipapp.initialize(["--no-term-title"])
  File "<decorator-gen-113>", line 2, in initialize
  File "/home/alan/.local/lib/python3.8/site-packages/traitlets/config/application.py", line 87, in catch_config_error
    return method(app, *args, **kwargs)
  File "/home/alan/.local/lib/python3.8/site-packages/IPython/terminal/ipapp.py", line 308, in initialize
    super(TerminalIPythonApp, self).initialize(argv)
  File "<decorator-gen-7>", line 2, in initialize
  File "/home/alan/.local/lib/python3.8/site-packages/traitlets/config/application.py", line 87, in catch_config_error
    return method(app, *args, **kwargs)
  File "/home/alan/.local/lib/python3.8/site-packages/IPython/core/application.py", line 450, in initialize
    self.parse_command_line(argv)
  File "/home/alan/.local/lib/python3.8/site-packages/IPython/terminal/ipapp.py", line 303, in parse_command_line
    return super(TerminalIPythonApp, self).parse_command_line(argv)
  File "<decorator-gen-4>", line 2, in parse_command_line
  File "/home/alan/.local/lib/python3.8/site-packages/traitlets/config/application.py", line 87, in catch_config_error
    return method(app, *args, **kwargs)
  File "/home/alan/.local/lib/python3.8/site-packages/traitlets/config/application.py", line 538, in parse_command_line
    self.cli_config = deepcopy(loader.load_config())
  File "/home/alan/.local/lib/python3.8/site-packages/traitlets/config/loader.py", line 745, in load_config
    self._create_parser(aliases, flags)
  File "/home/alan/.local/lib/python3.8/site-packages/traitlets/config/loader.py", line 757, in _create_parser
    self.parser = ArgumentParser(*self.parser_args, **self.parser_kw)
  File "/usr/lib/python3.8/argparse.py", line 1672, in __init__
    prog = _os.path.basename(_sys.argv[0])
IndexError: list index out of range