@dino99 - The only way to skip a release when upgrading is to go from one LTS to another LTS, which in this case would be from 14.04 to 16.04., so it is not possible to upgrade from 14.04 to 15.04 as you suggest. Additionally, the upgrade did try to proceed and encountered an error which is unrelated to Utopic being End of Life.
@dino99 - The only way to skip a release when upgrading is to go from one LTS to another LTS, which in this case would be from 14.04 to 16.04., so it is not possible to upgrade from 14.04 to 15.04 as you suggest. Additionally, the upgrade did try to proceed and encountered an error which is unrelated to Utopic being End of Life.