code: def find_executable(name, names=None, required=True):
      
      path_from_env = os.environ.get(name.upper())
      if path_from_env is not None:
          return path_from_env
      names = [name] + (names or [])
      for _name in names:
          if osp.isabs(_name):
              return _name
          paths = os.environ.get('PATH', '').split(os.pathsep)
          eax = find_in_paths(_name, paths)
          if eax:
              return eax
      if required:
          raise NameError('Could not find %s executable' % name)
      else:
          return name
docs: Utility function to find an executable in PATH
      name: program to find. Use given value if absolute path
  
      names: list of additional names. For instance
  
         >>> find_executable('sed', names=['gsed'])
  
      required: If True, then the function raises an Exception
      if the program is not found else the function returns name if
      the program is not found.