title: python keyError at JSON parsing
body: <p>I am trying to use Google Books Python API Client. Here is my simple code snippet:</p>
  
  <pre><code>for book in response.get('items', []):
      if not book['volumeInfo']['title'] or not book['volumeInfo']['authors']:
          continue
      else:
          print 'Title: %s, Author: %s' % (book['volumeInfo']['title'], book['volumeInfo']['authors'])
  </code></pre>
  
  <p>I am trying to get metadata from a list of books based on a keyword. However,  It gives me </p>
  
  <pre><code>KeyError: 'authors'
  </code></pre>
  
  <p>I checked and found out that the JSON response does not have an "authors" field for a specific book. I tried to skip that book with the if else statement above, but it didn't work. How can I avoid from such errors when there isn't a field in the JSON response as I expect? </p>