title: NodeJS JWT Sign.sign TypeError: Not a buffer
body: <p>I am currently working on a node.js app which should create events in google calendar.
  On my machine (OS X 10.9.2) it works well, but on another machine (Debian 7 Wheezy 64-bit) it does not work. Both have installed the same node.js version: v0.10.26. I always get the following error:</p>
  
  <pre><code>crypto.js:398
  var ret = this._binding.sign(toBuf(key));
                        ^
  TypeError: Not a buffer
  at Sign.sign (crypto.js:398:27)
  at createRS256Signature (/path/to/node_app/node_modules/googleapis/node_modules/gapitoken/node_modules/jws/index.js:75:58)
  at jwsRS256Sign (/path/to/node_app/node_modules/googleapis/node_modules/gapitoken/node_modules/jws/index.js:68:21)
  at Object.jwsSign [as sign] (/path/to/node_app/node_modules/googleapis/node_modules/gapitoken/node_modules/jws/index.js:32:12)
  at GAPI.getAccessToken (/path/to/node_app/node_modules/googleapis/node_modules/gapitoken/gapitoken.js:56:25)
  at GAPI.getToken (/path/to/node_app/node_modules/googleapis/node_modules/gapitoken/gapitoken.js:35:14)
  at JWT.refreshToken_ (/path/to/node_app/node_modules/googleapis/lib/auth/jwtclient.js:83:13)
  at /path/to/node_app/node_modules/googleapis/lib/auth/jwtclient.js:64:12
  at /path/to/node_app/node_modules/googleapis/node_modules/gapitoken/gapitoken.js:20:17
  at fs.js:266:14
  </code></pre>
  
  <p>The code that causes this error:</p>
  
  <pre><code>this.jwt = new googleapis.auth.JWT(
      SERVICE_ACCOUNT_EMAIL,
      SERVICE_ACCOUNT_KEY_FILE,
      null,
      ['https://www.googleapis.com/auth/calendar', 'https://www.googleapis.com/auth/calendar.readonly']);
  </code></pre>
  
  <p>SERVICE_ACCOUNT_KEY_FILE is the path to my .pem keyfile, which also can be found by the application.</p>
  
  <p>Everything works locally, but not on the Debian machine. Do I have to install some dependencies or something similar?</p>
  
  <p>EDIT1: I also tried passing the key as a string via the third argument, but that didn't work either.</p>
  
  <p>Thank you!</p>