Add method name in Unknown RPC error.

Bug=26883519

Change-Id: I371e2104d1245f797a2c994fa45c2889523ff101
diff --git a/sl4a/Common/src/com/googlecode/android_scripting/jsonrpc/JsonRpcServer.java b/sl4a/Common/src/com/googlecode/android_scripting/jsonrpc/JsonRpcServer.java
index 601b967..5bdd99a 100644
--- a/sl4a/Common/src/com/googlecode/android_scripting/jsonrpc/JsonRpcServer.java
+++ b/sl4a/Common/src/com/googlecode/android_scripting/jsonrpc/JsonRpcServer.java
@@ -91,7 +91,7 @@
 
             MethodDescriptor rpc = receiverManager.getMethodDescriptor(method);
             if (rpc == null) {
-                send(writer, JsonRpcResult.error(id, new RpcError("Unknown RPC.")), UID);
+                send(writer, JsonRpcResult.error(id, new RpcError("Unknown RPC: " + method)), UID);
                 continue;
             }
             try {