Check the last line of warning, for me it looked like this
Users/user/Documents/Dev/MyiOSProject/Project/Project/Supporting Files/Base.lproj/Storyboard.storyboard:dse-nb-xgC: warning: 2 conflicting constraints
The ID at the end identifies the object causing the problem. Right click on storyboard and open as source code, then look for the object with ID e.g. dse-nb-xgC
Look for the container of that line to identify the controller and either go to resolve your problem manually or delete the line and start from there