Hello!

Thanks a lot for working on this!! :-D

I get a warning during compilation:

guix/cve.scm:328:18: warning: possibly unbound variable `cve-item-base-
severity'

I also just tried it on patch package and it fails:

$ ./pre-inst-env guix lint -c cve patch
Backtrace:atch@2.7.6 [cve]...
In ice-9/boot-9.scm:
  1736:10 18 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
          17 (apply-smob/0 #<thunk 7f5c56304520>)
In ice-9/boot-9.scm:
    718:2 16 (call-with-prompt _ _ #<procedure default-prompt-handle…>)
In ice-9/eval.scm:
    619:8 15 (_ #(#(#<directory (guile-user) 7f5c56307c80>)))
In guix/ui.scm:
  2164:12 14 (run-guix-command _ . _)
In ice-9/boot-9.scm:
  1736:10 13 (with-exception-handler _ _ #:unwind? _ # _)
  1731:15 12 (with-exception-handler #<procedure 7f5c52ccde40 at ic…>
…)
In srfi/srfi-1.scm:
    634:9 11 (for-each #<procedure 7f5c52ccb620 at guix/scripts/lin…>
…)
In guix/scripts/lint.scm:
     65:4 10 (run-checkers #<package patch@2.7.6 gnu/packages/base.…>
…)
In srfi/srfi-1.scm:
    634:9  9 (for-each #<procedure 7f5c43b5df30 at guix/scripts/lin…>
…)
In guix/scripts/lint.scm:
    74:21  8 (_ _)
In guix/lint.scm:
   1205:4  7 (check-vulnerabilities #<package patch@2.7.6 gnu/packa…>
…)
   1151:9  6 (_ _)
In unknown file:
           5 (force #<promise #<procedure 7f5c5303cab8 at guix/lint.…>)
In guix/lint.scm:
   1134:2  4 (_)
   1093:2  3 (call-with-networking-fail-safe _ _ _)
In ice-9/boot-9.scm:
  1736:10  2 (with-exception-handler _ _ #:unwind? _ # _)
  1669:16  1 (raise-exception _ #:continuable? _)
  1667:16  0 (raise-exception _ #:continuable? _)

ice-9/boot-9.scm:1667:16: In procedure raise-exception:
Throw to key `match-error' with args `("match" "no matching pattern" (v
"CVE-2021-0212" (("contrail_networking" (< "1911.31")))))'.