Previously, "guix package -r something-not-installed" would silently
complete. Now an error is raised.
* guix/profiles.scm (&unmatched-pattern-error): New condition type.
(manifest-matching-entries): Rewrite to raise an error when one of
PATTERNS is not matched.
* guix/ui.scm (call-with-error-handling): Handle 'unmatched-pattern-error?'.
* tests/guix-package.sh: Add test.
* tests/profiles.scm ("manifest-matching-entries"): Don't try to remove
unmatched pattern.
("manifest-matching-entries, no match"): New test.
("manifest-transaction-effects"): Remove 'remove' field.
