Fix an invalid invocation of [new PubspecException].

sdk/lib/_internal/pub/lib/src/pubspec.dart

Index: sdk/lib/_internal/pub/lib/src/pubspec.dart
diff --git a/sdk/lib/_internal/pub/lib/src/pubspec.dart b/sdk/lib/_internal/pub/lib/src/pubspec.dart
index 87ec55d92d84610c57783fbaad15a03179591ec2..e6344a4db01736472adc8f0c96034a9f3b97b14a 100644
--- a/sdk/lib/_internal/pub/lib/src/pubspec.dart
+++ b/sdk/lib/_internal/pub/lib/src/pubspec.dart
@@ -225,7 +225,7 @@ class Pubspec {
       return new Pubspec.parse(readTextFile(pubspecPath), sources,
           expectedName: expectedName, location: pubspecUri);
     } on YamlException catch (error) {
-      throw new PubspecException("Error parsing $pubspecPath: $error");
+      throw new PubspecException(expectedName, pubspecUri, error.toString());
     }
   }