I've been receiving this warnings every time I compile a document with tufte-latex class:
** WARNING ** Failed to convert input string to UTF16...
Nothing happens, the document compiles fine, but what do those warnings mean?
Here is a minimum working example - it works fine with pdfTeX, but produces the warning with XeTeX:
\documentclass{tufte-book}
\begin{document}
\part{A Tale of Two Cities}
\end{document}