configure: error: Package requirements (libunbound >= 1.16) were not met:
Package 'libevent', required by 'libunbound', not found
This looks like a bug in libunbound - it is missing a dependency on libevent, which is then not pulled in, and in turn causes our build to fail.
This is the bug I raised when I originally hit the problem:
Installing libevent manually is the workaround, obviously not going to work for an automated build.