How to use the fbs.builtin_commands._util.require_existing_project function in fbs

def test():
    """
    Execute your automated tests
    """
    require_existing_project()
    sys.path.append(path('src/main/python'))
    suite = TestSuite()
    test_dirs = SETTINGS['test_dirs']
    for test_dir in map(path, test_dirs):
        sys.path.append(test_dir)
        try:
            dir_names = listdir(test_dir)
        except FileNotFoundError:
            continue
        for dir_name in dir_names:
            dir_path = join(test_dir, dir_name)
            if isfile(join(dir_path, '__init__.py')):
                suite.addTest(defaultTestLoader.discover(
                    dir_name, top_level_dir=test_dir
                ))
    has_tests = bool(list(suite))

def repo():
    """
    Generate files for automatic updates
    """
    require_existing_project()
    app_name = SETTINGS['app_name']
    pkg_name = app_name.lower()
    try:
        gpg_key = SETTINGS['gpg_key']
    except KeyError:
        raise FbsError(
            'GPG key for code signing is not configured. You might want to '
            'either\n'
            '    1) run `fbs gengpgkey` or\n'
            '    2) set "gpg_key" and "gpg_pass" in src/build/settings/.'
        )
    if is_ubuntu():
        from fbs.repo.ubuntu import create_repo_ubuntu
        if not SETTINGS['description']:
            _LOG.info(
                'Hint: Your app\'s "description" is empty. Consider setting it '

def freeze(debug=False):
    """
    Compile your code to a standalone executable
    """
    require_existing_project()
    if not _has_module('PyInstaller'):
        raise FbsError(
            "Could not find PyInstaller. Maybe you need to:\n"
            "    pip install PyInstaller==3.4"
        )
    # Import respective functions late to avoid circular import
    # fbs <-> fbs.freeze.X.
    app_name = SETTINGS['app_name']
    if is_mac():
        from fbs.freeze.mac import freeze_mac
        freeze_mac(debug=debug)
        executable = 'target/%s.app/Contents/MacOS/%s' % (app_name, app_name)
    else:
        executable = join('target', app_name, app_name)
        if is_windows():
            from fbs.freeze.windows import freeze_windows

def release():
    """
    Bump version and run clean,freeze,...,upload
    """
    require_existing_project()
    version = SETTINGS['version']
    next_version = _get_next_version(version)
    release_version = prompt_for_value('Release version', default=next_version)
    activate_profile('release')
    SETTINGS['version'] = release_version
    log_level = _LOG.level
    if log_level == logging.NOTSET:
        _LOG.setLevel(logging.WARNING)
    try:
        clean()
        freeze()
        if is_windows() and _has_windows_codesigning_certificate():
            sign()
        installer()
        if (is_windows() and _has_windows_codesigning_certificate()) or \
            is_arch_linux() or is_fedora():

def run():
    """
    Run your app from source
    """
    require_existing_project()
    if not _has_module('PyQt5') and not _has_module('PySide2'):
        raise FbsError(
            "Couldn't find PyQt5 or PySide2. Maybe you need to:\n"
            "    pip install PyQt5==5.9.2 or\n"
            "    pip install PySide2==5.12.2"
        )
    env = dict(os.environ)
    pythonpath = path('src/main/python')
    old_pythonpath = env.get('PYTHONPATH', '')
    if old_pythonpath:
        pythonpath += os.pathsep + old_pythonpath
    env['PYTHONPATH'] = pythonpath
    subprocess.run([sys.executable, path(SETTINGS['main_module'])], env=env)

def upload():
    """
    Upload installer and repository to fbs.sh
    """
    require_existing_project()
    try:
        username = SETTINGS['fbs_user']
        password = SETTINGS['fbs_pass']
    except KeyError as e:
        raise FbsError(
            'Could not find setting "%s". You may want to invoke one of the '
            'following:\n'
            ' * fbs register\n'
            ' * fbs login'
            % (e.args[0],)
        ) from None
    _upload_repo(username, password)
    app_name = SETTINGS['app_name']
    url = lambda p: 'https://fbs.sh/%s/%s/%s' % (username, app_name, p)
    message = 'Done! '
    pkg_name = app_name.lower()

def gengpgkey():
    """
    Generate a GPG key for Linux code signing
    """
    require_existing_project()
    if exists(_DEST_DIR):
        raise FbsError('The %s folder already exists. Aborting.' % _DEST_DIR)
    try:
        email = prompt_for_value('Email address')
        name = prompt_for_value('Real name', default=SETTINGS['author'])
        passphrase = prompt_for_value('Key password', password=True)
    except KeyboardInterrupt:
        print('')
        return
    print('')
    _LOG.info('Generating the GPG key. This can take a little...')
    _init_docker()
    args = ['run', '-t']
    if exists('/dev/urandom'):
        # Give the key generator more entropy on Posix:
        args.extend(['-v', '/dev/urandom:/dev/random'])