error[E0080]: evaluation panicked: no-spec explanation must not be empty; use no_spec!("reason");
 --> tests/ui/fail_empty_explanation.rs:3:1
  |
3 | no_spec!("   ");
  | ^^^^^^^^^^^^^^^ evaluation of `_` failed here
  |
  = note: this error originates in the macro `$crate::panic::panic_2021` which comes from the expansion of the macro `no_spec` (in Nightly builds, run with -Z macro-backtrace for more info)