Rework "analysis.updateContent" analysis server request.

pkg/analysis_server/test/integration/integration_tests.dart

Index: pkg/analysis_server/test/integration/integration_tests.dart
diff --git a/pkg/analysis_server/test/integration/integration_tests.dart b/pkg/analysis_server/test/integration/integration_tests.dart
index 7dfd240711385b6b66cd21f4c3420047f05ecbe7..dbd26a72f4485857e07da8d05a53be2e54eb4d35 100644
--- a/pkg/analysis_server/test/integration/integration_tests.dart
+++ b/pkg/analysis_server/test/integration/integration_tests.dart
@@ -570,7 +570,7 @@ class Server {
           if (messageAsMap.containsKey('error')) {
             // TODO(paulberry): propagate the error info to the completer.
             completer.completeError(new UnimplementedError(
-                'Server responded with an error'));
+                'Server responded with an error: ${JSON.encode(message)}'));
           } else {
             completer.complete(messageAsMap['result']);
           }