title: Cloud Datastore returns 413 Request Entity Too Large
body: <p>The datastore errors documentation doesn't list that this error happens. It's also not the same error that you get if you assign an individual value something too long (e.g. a blob > 1MB).</p>
  
  <p>I was able to work around it by reducing the number of inserts in my batch insert, but what's the actual limit being exceeded?</p>