build.webkit.org builders should run the python/perl unit tests The commit-queue does now as of http://trac.webkit.org/changeset/52989 But the main builders do not. Seems it would be useful to add (and shouldn't add more than a couple seconds). build.webkit.org config can be found here: http://trac.webkit.org/browser/trunk/WebKitTools/BuildSlaveSupport/build.webkit.org-config
bug 32189 is very similar.
*** Bug 28618 has been marked as a duplicate of this bug. ***
This has long been fixed.