The plasma-workspace test suite require a rebuild, what takes too long.
It currently times out on ci.debian.net.

Please have in mind that the purpose of autopkgtest is testing installed
binary packages, so a full rebuild is usually not necessary. If any part
of test suite needs to be compiled, please building only the required
subset, or ship the tests in a binary package.

I am blacklisting plasma-workspace, and will revisit that when this bug
is closed.