errors on upgrading to 2018.3

I just upgraded to 2018.3 and now i can't run my project. I am getting the following errors:

Assets/PostProcessing/Editor/PropertyDrawers/MinDrawer.cs(6,34): error CS0104: MinAttribute' is an ambiguous reference between UnityEngine.MinAttribute' and `UnityEngine.PostProcessing.MinAttribute'

Never had PostProcessing directory before. Do I need to delete this directory?

Thanks