module 'babble' has no attribute 'launcher'

[SkySailing]

error info show as blow

(base) zhangsan@zhangsan-Pro python-pex-tutorial % ./babble.pex                                                              
Traceback (most recent call last):
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/dist_metadata.py", line 726, in resolve
    return cast("Callable[[], Any]", functools.reduce(getattr, self._attrs, module))
AttributeError: module 'babble' has no attribute 'launcher'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/zhangsan/opt/miniconda3/lib/python3.9/runpy.py", line 197, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/Users/zhangsan/opt/miniconda3/lib/python3.9/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/__main__.py", line 103, in <module>
    bootstrap_pex(__entry_point__, execute=__execute__, venv_dir=__venv_dir__)
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/pex_bootstrapper.py", line 601, in bootstrap_pex
    pex.PEX(entry_point).execute()
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/pex.py", line 540, in execute
    sys.exit(self._wrap_coverage(self._wrap_profiling, self._execute))
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/pex.py", line 447, in _wrap_coverage
    return runner(*args)
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/pex.py", line 478, in _wrap_profiling
    return runner(*args)
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/pex.py", line 567, in _execute
    return self.execute_entry(
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/pex.py", line 749, in execute_entry
    return self.execute_entry_point(entry_point)
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/pex.py", line 766, in execute_entry_point
    runner = entry_point.resolve()
  File "/Users/zhangsan/.pex/unzipped_pexes/2c6f9cffd420abeb2540180c3858f97754c846ad/.bootstrap/pex/dist_metadata.py", line 728, in resolve
    raise ImportError(
ImportError: Could not resolve launcher in <module 'babble' from '/Users/zhangsan/.pex/installed_wheels/402a2f03c49f5d6a0519911e0373834780d3d571ab0a44a57fcf21d100247676/babble-2020.1.6-py3-none-any.whl/babble/__init__.py'>: module 'babble' has no attribute 'launcher'