ctest should check if CDash supports the Done part before submitting it
As noted in this comment, if submitting the new Done part introduced with CMake 3.14 to a CDash server that doesn't understand it (which will be most existing CDash servers), a fairly unhelpful message is added to the log file on the CDash server, e.g.:
[2019-02-17 09:07:57] cdash.ERROR: error: could not create handler based on xml content {"function":"ctest_parse","pid":7434}
Every job submission that does this will add such a line to the CDash log, which normally would be fairly quiet. For a busy CDash server, the potential for this to dramatically increase the volume of the CDash log seems high. If ctest has the ability to tell what version of CDash it is talking to, it should be able to only submit the Done part if it knows the CDash server will understand it.