title: Twilio function giving invalid content-type error
body: <p>I'm trying to make an outgoing call to an automated phone system, but I'm running into a content-type error. I don't understand what a content-type error is, so if someone could help me understand that would be great. Here's the code I have right now.</p>
  
  <pre><code>exports.handler = function(context, event, callback) {
  
      const accountSid = 'AC5ca0acd115283b6d7ed38279';
      const authToken = 'not my real auth token';
      const client = require('twilio')(accountSid, authToken);
  
      client.calls
            .create({
               to: '+14805402416',
               from: '+18448345500',
               record: 'True',
               transcribe: 'True',
               sendDigits: 'wwww1wwww123#wwww1', // w's are .5 second delays to navigate pauses in the automated system 
                                                 // '1' - English, '123#' - PIN #, '1' - Confirm PIN
             });
  
      callback(null, client);
  };
  </code></pre>