Raymond asked on IRC why this work is being back-ported.  The answer is that it is being forward-ported rather than back-ported.  The trace module had no unittests in either 2.x or 3.x and was very buggy in 3.x.  Presumably, 2.x version saw more use and was likely to be more correct than 3.x, so we decided to start with adding unit tests to 2.7 and then port the tests to 3.x while fixing the bugs.  See msg111134.

This does not necessarily mean that we need to include 3.1. It may be appropriate to limit what is going to 3.1 to tests that support bug fixes.

If nobody raises an objection, I am going to close this issue by removing list comprehension test from 3.1 and will open a separate "interpreter core" issue for line tracing inconsistencies.