docs: def shell():
      '''
      Return the default shell to use on this system
      '''
      # Provides:
      #   shell
      if salt.utils.platform.is_windows():
          env_var = 'COMSPEC'
          default = r'C:\Windows\system32\cmd.exe'
      else:
          env_var = 'SHELL'
          default = '/bin/sh'
  
      return {'shell': os.environ.get(env_var, default)}