Use document’s url_fetcher for attachments

Also force HTML attachments to be detected as URLs so that url_fetcher is
always used.

weasyprint/html.py

@@ -281,7 +281,9 @@ def get_html_metadata(html):
             if url is None:
                 LOGGER.error('Missing href in <link rel="attachment">')
             else:
-                attachment = Attachment(url=url, description=attachment_title)
+                attachment = Attachment(
+                    url=url, description=attachment_title,
+                    url_fetcher=html.url_fetcher)
                 attachments.append(attachment)
     return {
         'title': title,

weasyprint/pdf/__init__.py

@@ -249,7 +249,8 @@ def generate_pdf(document, target, zoom, **options):
     if options['attachments']:
         for attachment in options['attachments']:
             if not isinstance(attachment, Attachment):
-                attachment = Attachment(attachment)
+                attachment = Attachment(
+                    attachment, url_fetcher=document.url_fetcher)
             attachments.append(attachment)
     pdf_attachments = []
     for attachment in attachments:

weasyprint/pdf/anchors.py

@@ -252,8 +252,10 @@ def add_annotations(links, matrix, document, pdf, page, annot_files, compress):
             # TODO: Use the title attribute as description. The comment
             # above about multiple regions won't always be correct, because
             # two links might have the same href, but different titles.
+            attachment = Attachment(
+                url=annot_target, url_fetcher=document.url_fetcher)
             annot_files[annot_target] = write_pdf_attachment(
-                pdf, Attachment(annot_target), compress)
+                pdf, attachment, compress)
         annot_file = annot_files[annot_target]
         if annot_file is None:
             continue