Hmm, yes, sounds more like a separate issue than something to add to this ticket. It worked before (starting with Py2.5, which was the first Python version to support relative imports) and only stopped working in 3.3 now.

The .srctree test file basically just unfolds into a file system hierarchy with each file named as in the preceding "magical" comment. The commands in the lines before the first comment line are then executed for the test (usually: build module with distutils, import it, do something with it).