Warn about removal of deprecated format strings (#33829)

Co-authored-by: becker33 <becker33@users.noreply.github.com>

lib/spack/spack/spec.py

@@ -4418,7 +4418,10 @@ def old_format(self, format_string="$_$@$%@+$+$=", **kwargs):
         TODO: allow, e.g., ``$6#`` to customize short hash length
         TODO: allow, e.g., ``$//`` for full hash.
         """
-
+        tty.warn(
+            "Using the old Spec.format method."
+            " This method was deprecated in Spack v0.15 and will be removed in Spack v0.20"
+        )
         color = kwargs.get("color", False)
 
         # Dictionary of transformations for named tokens

lib/spack/spack/test/directory_layout.py

@@ -59,7 +59,7 @@ def test_yaml_directory_layout_parameters(tmpdir, default_mock_concretization):
     arch_scheme = (
         "{architecture.platform}/{architecture.target}/{architecture.os}/{name}/{version}/{hash:7}"
     )
-    ns_scheme = "${ARCHITECTURE}/${NAMESPACE}/${PACKAGE}-${VERSION}-${HASH:7}"
+    ns_scheme = "${architecture}/${namespace}/${name}-${version}-${hash:7}"
     arch_ns_scheme_projections = {"all": arch_scheme, "python": ns_scheme}
     layout_arch_ns = DirectoryLayout(str(tmpdir), projections=arch_ns_scheme_projections)