Fix error in processing dart-ext urls with a relative path.

sdk/lib/core/uri.dart

Index: sdk/lib/core/uri.dart
diff --git a/sdk/lib/core/uri.dart b/sdk/lib/core/uri.dart
index d2e2a7ad865ae6238d9a6128da9e8557654a490d..41130ad08cea677b05826f3f4574e48842324bf7 100644
--- a/sdk/lib/core/uri.dart
+++ b/sdk/lib/core/uri.dart
@@ -390,9 +390,9 @@ class Uri {
     segments.skip(firstSegment).forEach((segment) {
       if (segment.contains(new RegExp(r'["*/:<>?\\|]'))) {
         if (argumentError) {
-          throw new ArgumentError("Illegal character in path}");
+          throw new ArgumentError("Illegal character in path");
         } else {
-          throw new UnsupportedError("Illegal character in path}");
+          throw new UnsupportedError("Illegal character in path");
         }
       }
     });