Handle symbol literals in closed_world2_test

pkg/compiler/lib/src/resolution/resolution_strategy.dart

Index: pkg/compiler/lib/src/resolution/resolution_strategy.dart
diff --git a/pkg/compiler/lib/src/resolution/resolution_strategy.dart b/pkg/compiler/lib/src/resolution/resolution_strategy.dart
index b71bd4c056d0f2f2ce23a81b10703ac096c2ae92..b964cbf7fe8c30bff97d0fee58da4c8b539ac70a 100644
--- a/pkg/compiler/lib/src/resolution/resolution_strategy.dart
+++ b/pkg/compiler/lib/src/resolution/resolution_strategy.dart
@@ -353,7 +353,7 @@ class _CompilerElementEnvironment implements ElementEnvironment {
     ClassElement cls = library.implementation.findLocal(name);
     if (cls == null && required) {
       throw new SpannableAssertionFailure(
-          cls,
+          library,
           "The library '${library.libraryName}' does not "
           "contain required class: '$name'.");
     }
@@ -382,7 +382,7 @@ class _CompilerElementEnvironment implements ElementEnvironment {
     }
     if (library == null && required) {
       throw new SpannableAssertionFailure(
-          library, "The library '${uri}' was not found.");
+          NO_LOCATION_SPANNABLE, "The library '${uri}' was not found.");
     }
     return library;
   }