Fix interpolation in warning message. :(

utils/pub/validator/name.dart

Index: utils/pub/validator/name.dart
diff --git a/utils/pub/validator/name.dart b/utils/pub/validator/name.dart
index fb2c418fbaaf44b1bc050f93334e08515079ef03..22cb8cb6276d41a574b213d60d8c0fbcfbe28458 100644
--- a/utils/pub/validator/name.dart
+++ b/utils/pub/validator/name.dart
@@ -35,7 +35,7 @@ class NameValidator extends Validator {
       if (libraries.length == 1) {
         var libName = path.basenameWithoutExtension(libraries[0]);
         if (libName == entrypoint.root.name) return;
-        warnings.add('The name of "$libraries[0]", "$libName", should match '
+        warnings.add('The name of "${libraries[0]}", "$libName", should match '
             'the name of the package, "${entrypoint.root.name}".\n'
             'This helps users know what library to import.');
       }