The release of Xcode 11.3.0 has maxed out the space on our macOS host drives. In order to add capacity for this image, we must drop support for Xcode 8.3.3, our least-used image (0.3% of jobs used 8.3.3 over the last 7 days).
We will remove support for Xcode 8.3.3 on January 10, 2019. We will be emailing the customers that have built on 8.3.3 over the last two weeks, and our team is working to follow up with the limited set of customers that are using the Xcode 8.3.3 image on their master branch.
Please open a support ticket on the CircleCI Support Website or reach out to your Customer Success Manager if you have any questions or comments.
All versions of Xcode currently supported on CircleCI are listed in the CircleCI Testing iOS Applications docs.