Add executable permissions to a file.

    Args:
      metadata_script: string, the path to the executable file.

def _MakeExecutable(self, metadata_script):
    """Add executable permissions to a file.

    Args:
      metadata_script: string, the path to the executable file.
    """
    mode = os.stat(metadata_script).st_mode
    os.chmod(metadata_script, mode | stat.S_IEXEC)