tests_secrets_cli: improve assertion message for pgp key

pkgs/clan-cli/clan_cli/tests/test_secrets_cli.py

@@ -982,7 +982,10 @@ def test_secrets_key_generate_gpg(
                 ]
             )
         assert "age private key" not in output.out
-        assert re.match(r"PGP key.+is already set", output.err) is not None
+
+        assert re.match(r"PGP key.+is already set", output.err), (
+            f"expected /PGP key.+is already set/ =~ {output.err}"
+        )
 
         with capture_output as output:
             cli.run(