Load PDF cover and inline images from disk via custom WeasyPrint url_fetcher

@@ -23,7 +23,9 @@ from flask import (    send_from_directory,    url_for,)from weasyprint import HTMLfrom urllib.parse import unquote, urlparsefrom weasyprint import HTML, default_url_fetcherapp = Flask(__name__)app.config["SEND_FILE_MAX_AGE_DEFAULT"] = 31536000

@@ -299,6 +301,20 @@ def blog_post(slug):    )def pdf_url_fetcher(url):    path = unquote(urlparse(url).path)    local_roots = {        "/content/images/": os.path.join(CONTENT_DIR, "images"),        "/static/": app.static_folder,    }    for prefix, root in local_roots.items():        if path.startswith(prefix):            file_path = os.path.join(root, path[len(prefix):])            if os.path.isfile(file_path):                return {"file_obj": open(file_path, "rb")}    return default_url_fetcher(url)@app.route("/posts/<slug>/pdf/")def blog_post_pdf(slug):    post = POSTS_BY_SLUG.get(slug)

@@ -308,6 +324,7 @@ def blog_post_pdf(slug):    pdf = HTML(        string=html_content,        base_url=request.url_root,        url_fetcher=pdf_url_fetcher,    ).write_pdf()    return Response(        pdf,