Everytime i ran "jupyter notebook" on my mac os, why always got this error?

case:

1. i have python2.x and i installed python3.7 (so, i have two commands here)
2. i installed jupyter with pip
3. when i put jupyter notebook command, i always got these error

Error:

```
Traceback (most recent call last):
File "/Library/Frameworks/Python.framework/Versions/3.7/bin/jupyter-notebook", line 11, in <module>
  sys.exit(main())
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/jupyter_core/application.py", line 266, in launch_instance
  return super(JupyterApp, cls).launch_instance(argv=argv, **kwargs)
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/traitlets/config/application.py", line 658, in launch_instance
  app.start()
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/notebook/notebookapp.py", line 1697, in start
  browser = webbrowser.get(self.browser or None)
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/webbrowser.py", line 42, in get
  register_standard_browsers()
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/webbrowser.py", line 531, in register_standard_browsers
  raw_result = subprocess.check_output(cmd, stderr=subprocess.DEVNULL)
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py", line 376, in check_output
  **kwargs).stdout
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py", line 453, in run
  with Popen(*popenargs, **kwargs) as process:
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py", line 756, in __init__
  restore_signals, start_new_session)
File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/subprocess.py", line 1499, in _execute_child
  raise child_exception_type(errno_num, err_msg, err_filename)
NotADirectoryError: [Errno 20] Not a directory: 'xdg-settings'

```