How to stop file-roller from outputting anything and hanging on the process

I'm writing a program that uses file-roller to extract an ISO file. However I keep getting a warning and I don't want to see this warning. Also file-roller hangs after this warning. Gtk-Message: GtkDialog mapped without transient parent. This is discouraged. Once this hits, file-roller will just hang and not do anything. I'm using file-roller through the command line with file-roller -e <PATH> <ISO IMAGE>. My question is simple, how can I disable the warnings and the stdout on the command and stop the process from hanging when a warning hits?

Script:

def unzip_iso(filepath, verbose=False, directory_name="ISO_dir"):
    """
      Unzip the ISO file into a directory

      :param filepath: the path to the ISO file
      :param verbose: verbosity output
      :param directory_name: the name of the ISO directory
      :return: True if it worked, False if it didn't
    """
    def create_rand_dir_name(chars=string.ascii_letters, verbose=False):
        """
          Create a random directory name
        """
        if verbose: LOGGER.debug("Creating random directory name..")
        retval = set()
        for _ in range(8):
            retval.add(random.choice(chars))
        return ''.join(list(retval))

    dirname = create_rand_dir_name(verbose=verbose)
    if verbose: LOGGER.debug("Creating directory: {}/{}/*..".format(directory_name, dirname))
    create_dir(directory_name + "/" + dirname)
    full_dir_path = os.getcwd() + "/" + directory_name + "/" + dirname
    if verbose: LOGGER.debug("Directory created, full path being saved to: {}..".format(full_dir_path))

    cmd = "file-roller -e {} {}".format(full_dir_path, filepath)
    if verbose: LOGGER.debug("Starting command: {}..".format(cmd))
    stdout_data = subprocess.check_call(cmd, shell=True)