title: DocumentApp.openById() fails with "Service unavailable"
body: <p>I'm sure I must be doing something silly, but I'm not seeing what it is.  How can I get the contents of a simple text file?  Does it need a .txt extension perhaps?  Perhaps it has something to do with how the file was created over a year ago?  </p>
  
  <p>The error was: 'Service unavailable: Docs (line 61, file "fileFuncs")'.  Line 61 is highlighted below.</p>
  
  <p>Thanks in advance for your help.</p>
  
  <pre><code>function testGetFile()
  {
  
  getFile("testGetFile", "WhoAmI");
  
  }
  
  function getFile(calledFrom, targetFile)
  {
  
  var root = DriveApp.getRootFolder();
  var files=root.getFiles();
  var numFiles=0;
  
   while (files.hasNext()) {
     var file = files.next();
     numFiles++;
     var filename = file.getName();
  
  
      if (filename == targetFile) {
  
        Logger.log("Success.  Found file: " + filename);
        Logger.log(' Number of files processed = '+numFiles+'\n\n');
  
        var fileId = file.getId();
        **var doc = DocumentApp.openById(fileId);       // Line 61:THIS FAILS with above error**
        var body=doc.getBody();
        var text=body.getText();
  
        Logger.log('text = '+text);// there it is         
  
        return text;
      }   
  
     } // while()
  
  return -1;
  }
  </code></pre>