title: Resource name must Start with a letter
body: <p>I am having this issue when I am having file with name <strong>01a.png</strong> under <code>res/drawable</code>. </p>
  
  <p>The error looks like:</p>
  
  <pre><code>Error: The resource name must start with a letter
  </code></pre>
  
  <p>I am using <code>build:gradle:2.1.2</code> and SDK version 24.</p>
  
  <p>Any solution to fix this without changing filename and without degrading <strong>SDK version</strong>?</p>