(TBR) Fix more failing tests

pkg/analysis_server/test/analysis/update_content_test.dart

Index: pkg/analysis_server/test/analysis/update_content_test.dart
diff --git a/pkg/analysis_server/test/analysis/update_content_test.dart b/pkg/analysis_server/test/analysis/update_content_test.dart
index b5d77c6ebcb2ae665a1b4ae054eaafac18aec1ae..788088f0d59be11fd4df7c9f89bc7914761d94e8 100644
--- a/pkg/analysis_server/test/analysis/update_content_test.dart
+++ b/pkg/analysis_server/test/analysis/update_content_test.dart
@@ -170,7 +170,7 @@ f() {}
         {'/project/main.dart': new AddContentOverlay('import "target.dart";')});
     await server.onAnalysisComplete;
     expect(filesErrors, {
-      '/project/main.dart': ["1: Target of URI does not exist: 'target.dart'"],
+      '/project/main.dart': ["1: Target of URI doesn't exist: 'target.dart'."],
       '/project/target.dart': []
     });
 
@@ -178,8 +178,8 @@ f() {}
         {'/project/target.dart': new AddContentOverlay('import "none.dart";')});
     await server.onAnalysisComplete;
     expect(filesErrors, {
-      '/project/main.dart': ["1: Unused import"],
-      '/project/target.dart': ["1: Target of URI does not exist: 'none.dart'"],
+      '/project/main.dart': ["1: Unused import."],
+      '/project/target.dart': ["1: Target of URI doesn't exist: 'none.dart'."],
       '/project/none.dart': []
     });
   }