Gutenberg post validation before saving

Question

I'm trying to add a post save validation in the Gutenberg editor in the case post excerpt is empty. What I have now is:

const { subscribe } = wp.data;

const unsubscribe = subscribe(() => {
    const editor = wp.data.select('core/editor');
    const notices = wp.data.select('core/notices');

    const isSavingPost = editor.isSavingPost();
    const isAutosavingPost = editor.isAutosavingPost();
    const didPostSaveRequestSucceed = editor.didPostSaveRequestSucceed();

    if (isSavingPost && !isAutosavingPost && didPostSaveRequestSucceed) {
        const postExcerpt = editor.getEditedPostAttribute('excerpt');

        if (postExcerpt.length !== 0) {
            editor.unlockPostSaving('excerpt-lock');
            notices.removeNotice('excerpt-lock');

            editor.savePost();
        }

        editor.lockPostSaving('excerpt-lock');
        notices.createNotice(
            'error',
            'Please add an excerpt',
            { id: 'excerpt-lock', isDismissible: false }
        );

        unsubscribe();
    }
});

But on posts save I get

Uncaught (in promise) TypeError: editor.lockPostSaving is not a function

I'm not sure what I'm missing. I looked at tons of examples in the GB repo, in various tutorials but nothing worked.