When i try to build a PDF from `xml2rfc` while i'm completely offline, i see these error messages: ``` $ xml2rfc sop.xml --pdf -o sop.pdf ERROR:weasyprint:Failed to load stylesheet at https://fonts.googleapis.com/css?family=Noto+Sans : URLError: <urlopen error [Errno -3] Temporary failure in name resolution> ERROR:weasyprint:Failed to load stylesheet at https://fonts.googleapis.com/css?family=Noto+Serif : URLError: <urlopen error [Errno -3] Temporary failure in name resolution> ERROR:weasyprint:Failed to load stylesheet at https://fonts.googleapis.com/css?family=Roboto+Mono : URLError: <urlopen error [Errno -3] Temporary failure in name resolution> $ ``` xml2rfc should do what it can to operate weasyprint in an offline mode, and certainly shouldn't depend on stylesheets that might go away (or change) at the whim of an unrelated network provider.