Fix for an error in the error handler.

pkg/analysis_server/lib/src/analysis_server.dart

Index: pkg/analysis_server/lib/src/analysis_server.dart
diff --git a/pkg/analysis_server/lib/src/analysis_server.dart b/pkg/analysis_server/lib/src/analysis_server.dart
index 2ad03fdf3bd3238c32d9a395288e584e401cafb8..7abc951841b17b8b61b080c0397280c77ff0e8da 100644
--- a/pkg/analysis_server/lib/src/analysis_server.dart
+++ b/pkg/analysis_server/lib/src/analysis_server.dart
@@ -435,8 +435,9 @@ class AnalysisServer {
           channel.sendResponse(exception.response);
           return;
         } catch (exception, stackTrace) {
-          RequestError error =
-              new RequestError(RequestErrorCode.SERVER_ERROR, exception);
+          RequestError error = new RequestError(
+              RequestErrorCode.SERVER_ERROR,
+              exception.toString());
           if (stackTrace != null) {
             error.stackTrace = stackTrace.toString();
           }