title: Protobuf Message to JSON conversion of bytes field converts string to base64?
body: <p>I have a proto file like below:</p>
  
  <pre><code>syntax = "proto2";
  package user;
  
  message user_message {
      required bytes   username = 1;
      optional string   phonenum  = 2;
      optional string   password  = 3;
  }
  </code></pre>
  
  <p>When I receive the message, that is serialised as a String from the sender. </p>
  
  <p>This I try to convert to a JSON object:</p>
  
  <pre><code>base_msg = msg_periodic_pb2.m_apps_message()
  base_msg.ParseFromString(message)
  base_msg = json_format.MessageToJson(base_msg)
  </code></pre>
  
  <p>When I print the base_msg, after converting the message to JSON the username gets converted to a base64 string. How can I avoid this?</p>