docs: def getPathOfExecutable(executable):
      """
      Returns the full path of the executable, or None if the executable
      can not be found.
      """
      exe_paths = os.environ['PATH'].split(':')
      for exe_path in exe_paths:
          exe_file = os.path.join(exe_path, executable)
          if os.path.isfile(exe_file) and os.access(exe_file, os.X_OK):
              return exe_file
      return None