title: A popup, "Failed to automatically update constraints" pops up in Xcode 6.3.1
body: <p>When I added a couple of controls in my viewcontroller in storyboard and click
   <em>Resolve Auto Layout Issues -> Reset to Suggested Constraints</em>.
  The following popup appears and I cannot perform auto layout constraints.</p>
  
  <p><img src="https://i.stack.imgur.com/KAlkU.png" alt="enter image description here"></p>
  
  <p>Though, when I remove the Prototype Cell (which has a couple of labels and an imageview) from my tableview then auto layout works fine. Any thoughts?</p>
  
  <p><strong>Edited:</strong>
  And manually adding constraints to individual elements work fine as well. After manually setting the image view inside prototype cell, the auto layout has started working fine without popping up that popup. So, maybe, sometime, it is hard for auto layout to figure out all these constraints itself.</p>