proc-macro-error 1.0.4

Almost drop-in replacement to panics in proc-macros
Documentation 
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error: unknown setting `trololo`, expected one of `assert_unwind_safe`, `allow_not_macro`, `proc_macro_hack`
 --> $DIR/unknown_setting.rs:3:57
  |
3 | #[proc_macro_error(allow_not_macro, assert_unwind_safe, trololo)]
  |                                                         ^^^^^^^