I get the same error. It seems this is an issue in upstream with Emacs 27.1:
https://github.com/racer-rust/emacs-racer/issues/136
bug#43752: emacs-racer fails to install
Tomás Ortín Fernández via Bug reports for GNU Guix Fri, 02 Oct 2020 09:38:30 -0700
- bug#43752: emacs-rac... Luis Felipe via Bug reports for GNU Guix
- bug#43752: emac... Tomás Ortín Fernández via Bug reports for GNU Guix
- bug#43752: ... Nicolas Goaziou
