protected final RpcResponse getErrorResponse(String msg, Exception e) throws IOException {
    ResponseHeader.Builder headerBuilder = ResponseHeader.newBuilder().setCallId(-1);
    ServerCall.setExceptionResponse(e, msg, headerBuilder);
    ByteBuffer headerBuf =
      ServerCall.createHeaderAndMessageBytes(null, headerBuilder.build(), 0, null);
    BufferChain buf = new BufferChain(headerBuf);
    return () -> buf;
  }
Has the request header and the request param and optionally encoded data buffer all in this one
array.
<p/>
Will be overridden in tests.
hbase-server/src/main/java/org/apache/hadoop/hbase/ipc/ServerRpcConnection.java