When converting a book without a cover in the source file, setting the "Use cover from source file" option creates a PDF without a cover, and without an error. Sadly, when converting a book WITH a cover in the source file, setting this option does not improve the situation.
It looks to me like src/calibre/ebooks/pdf/writer.py has a bug in insert_cover (line 174 in the downloaded source), where
Code:
printer = self.get_printer()
should be
Code:
printer = get_pdf_printer(self.opts)