really fix ui test errors for real

Author: canndrew

src/test/ui/feature-gate-exhaustive-patterns.stderr

@@ -4,4 +4,7 @@ error[E0005]: refutable pattern in local binding: `Err(_)` not covered
 LL |     let Ok(_x) = foo(); //~ ERROR refutable pattern in local binding
    |         ^^^^^^ pattern `Err(_)` not covered
 
+error: aborting due to previous error
+
+If you want more information on this error, try using "rustc --explain E0005"