In the regression test results for a bug fix to ASDF
(https://gitlab.common-lisp.net/asdf/asdf/-/jobs/63801), I see this
error which I don't understand at all:
```
Cannot unuse package #<"COMMON-LISP" package> from locked package
#<"PACKAGE-INFERRED-SYSTEM-TEST/SBCL-EXT-LOCK" package>.
```
The line that seems to be causing this is the following (in a test
system):
```
(defpackage package-inferred-system-test/sbcl-ext-lock
(:use :cl)
#+(or sbcl ecl) (:lock t)
(:export #:implemented-by-other-package))
```
More discussion about this is in ASDF Merge Request 226:
https://gitlab.common-lisp.net/asdf/asdf/-/merge_requests/226
The underlying issue is to try to make sure that implementation specific
`defpackage` extensions (like `:lock`) don't cause ASDF's `defpackage`
groveler to fail when working with package-defined systems.
Thanks for any advice!
