Deny warnings in doctests

Author: pitdicker

src/lib.rs

@@ -382,7 +382,7 @@
 //! Advanced time zone handling is not yet supported.
 //! For now you can try the [Chrono-tz](https://github.com/chronotope/chrono-tz/) crate instead.
 
-#![doc(html_root_url = "https://docs.rs/chrono/latest/")]
+#![doc(html_root_url = "https://docs.rs/chrono/latest/", test(attr(deny(warnings))))]
 #![cfg_attr(feature = "bench", feature(test))] // lib stability features as per RFC #507
 #![deny(missing_docs)]
 #![deny(missing_debug_implementations)]