In last six or so weeks Microsoft managed to release whole bunch of .NET Core 2.1 SDKs (Preview 2, Release Candidate 1, Early Access, RTM) and we tried all of them. By the end of these weeks my cluster of CI servers looked like a zoo. As everything was done in a hurry, there were servers with RC1 pretending to be Early Access ones. EA servers pretended to be RTM compatible, and the only RTM host we had was pretending to support everything. Don’t look at me funny. It happens.
The problem happened when I tried to cleanup the mess: removed P2, RC1 and EA SDK tags from release branches, deleted prerelease servers, forced remaining servers to tell exactly who they are and finally rolled out new VMs with latest and greatest .NET Core SDK 2.1 installed. Naturally, very first build failed.