Fix a couple broken tests in pub/validator_test.

utils/pub/package.dart

Index: utils/pub/package.dart
diff --git a/utils/pub/package.dart b/utils/pub/package.dart
index 8e96cbd243e699f5ca9401418ae5ee50d6c969b6..b7c2f9943a38659cedcb9c6f461ff85afdb4e9be 100644
--- a/utils/pub/package.dart
+++ b/utils/pub/package.dart
@@ -45,16 +45,17 @@ class Package {
   /// chosen.
   Future<String> get readmePath {
     return listDir(dir).then((entries) {
-      var readmes = entries.where((entry) => entry.contains(_README_REGEXP));
+      var readmes = entries.map(path.basename).
+          where((entry) => entry.contains(_README_REGEXP));
       if (readmes.isEmpty) return;
 
-      return readmes.min((readme1, readme2) {
+      return path.join(dir, readmes.min((readme1, readme2) {
         var extensions1 = ".".allMatches(readme1).length;
         var extensions2 = ".".allMatches(readme2).length;
         var comparison = extensions1.compareTo(extensions2);
         if (comparison != 0) return comparison;
         return readme1.compareTo(readme2);
-      });
+      }));
     });
   }