Update src/tools/lint-docs/src/lib.rs

Co-authored-by: Eric Huss <[email protected]>

Author: compiler-errors

src/tools/lint-docs/src/lib.rs

@@ -497,7 +497,10 @@ impl<'a> LintExtractor<'a> {
             let non_json: Vec<&str> =
                 stderr.lines().filter(|line| !line.starts_with('{')).collect();
             return Err(format!(
-                "lint `{}` is unstable and must be enabled in example. see:\n{}\n{}",
+                "did not find lint `{}` in output of example (got unknown_lints)\n\
+                Is the lint possibly misspelled, or does it need a `#![feature(...)]`?\n\
+                Output was:\n\
+                {}\n{}",
                 name,
                 rendered.join("\n"),
                 non_json.join("\n"),