Auto merge of #12732 - tompscanlan:12576-registry-error-msg, r=epage

more specific registry index not found msg

### What does this PR try to resolve?

covers #12576

### How should we test and review this PR?

test covers exact text, so a review and passing tests.

src/cargo/util/config/mod.rs

@@ -1548,7 +1548,10 @@ impl Config {
                 )
             })
         } else {
-            bail!("no index found for registry: `{}`", registry);
+            bail!(
+                "registry index was not found in any configuration: `{}`",
+                registry
+            );
         }
     }
 

tests/testsuite/source_replacement.rs

@@ -243,7 +243,7 @@ fn undefined_default() {
         .replace_crates_io(crates_io.index_url())
         .with_status(101)
         .with_stderr(
-            "[ERROR] no index found for registry: `undefined`
+            "[ERROR] registry index was not found in any configuration: `undefined`
 ",
         )
         .run();