title: Backstop timeout causes fatal, prevents any results: how can I get backstop / puppeteer to show which URL is failing?
body: <p>Running a backstop test, I get the following output and backstop fails to generate a report:</p>
  <pre><code>      COMMAND | Command &quot;test&quot; ended with an error after [195.665s]
        COMMAND | TimeoutError: waiting for target failed: timeout 30000ms exceeded
                      at Function.waitWithTimeout (/usr/local/lib/node_modules/backstopjs/node_modules/puppeteer/lib/helper.js:228:26)
                      at Browser.waitForTarget (/usr/local/lib/node_modules/backstopjs/node_modules/puppeteer/lib/Browser.js:214:27)
                      at Browser.&lt;anonymous&gt; (/usr/local/lib/node_modules/backstopjs/node_modules/puppeteer/lib/helper.js:112:23)
                      at ChromeLauncher.launch (/usr/local/lib/node_modules/backstopjs/node_modules/puppeteer/lib/Launcher.js:247:21)
                      at process._tickCallback (internal/process/next_tick.js:68:7)
  x Close Browser
  </code></pre>
  <p>How do I tell which scenario is failing, so that I can debug it?
  Puppeteer is the engine I'm using.</p>
  <p>** <strong>Update</strong>: I've noticed a pattern between these failing pages: most of them include iframes (mostly youtube). I've worked around the issue in most cases by instructing backstop to ignore iframes, by using the <code>removeSelectors</code> directive:</p>
  <pre><code>&quot;removeSelectors&quot;: [
    &quot;iframe&quot;
  ]
  </code></pre>
  <p>I'm not thrilled with this solution, so leaving open in case someone has a better answer.</p>