Improve error message for macro parsing failure
Improve error message for macro parsing failure

fable-compiler/Fable,fable-compiler/Fable,fable-compiler/Fable,markek/Fable,ncave/Fable,ncave/Fable,markek/Fable,ncave/Fable,ncave/Fable,ncave/Fable,markek/Fable,fable-compiler/Fable,fable-compiler/Fable,ncave/Fable,inosik/Fable,fable-compiler/Fable,ncave/Fable,inosik/Fable,fable-compiler/Fable