errors2.rs: update link to Rust book.
@@ -68,5 +68,5 @@ mod tests {
// `Err(something)`. This pattern is very common in Rust, though, so there's
// a `?` operator that does pretty much what you would make that match statement
// do for you! Take a look at this section of the Error Handling chapter:
-// https://doc.rust-lang.org/stable/book/second-edition/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
+// https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
// and give it a try!
