title: Postman: More descriptive tv4 validation error message
body: <p>I'm using <a href="https://www.getpostman.com/" rel="noreferrer">postman</a> to validate the schema of json data returned from an api.</p>
  
  <p>I have a test that runs through basic http validation, then ends with:</p>
  
  <pre><code>if (tv4.error){
      console.log("Validation failed: ", tv4.error);
  }
  </code></pre>
  
  <p>The error I get back is difficult to fathom.</p>
  
  <blockquote>
    <p>Validation failed: 12:22:41.316<br>
      Object:{}<br>
    message:"Invalid type:
    number (expected string)"<br>
    name:"ValidationError"<br>
    type:"Error"</p>
  </blockquote>
  
  <p>But I need to know which field the validation failed on. How can I get this info? The <a href="https://www.npmjs.com/package/tv4" rel="noreferrer">npm page for tv4</a> suggests that the error message should be more descriptive.</p>