[from pydev discussion] I agree with renaming current test_trace to test_sys_settrace. If sys.settrace does more than line tracing, and the additional actions are not currently tested in the general sys test, then they should be, eventually, by someone, in a different issue.

I see two reasons to start with 2.7. First, the 2.7 code should be better since it will not have errors introduced by the 3.x port. Second, if one file does not work for both 2.7 and 3.1/2, 2to3 is more tested than 3to2. If 2.6 is not to be targeted, you can use any of the new 3.x features backported to 2.7. The main problem for 3.1+ should be any new bugs uncovered, other than the one fixed in #9282. If features are added for 3.2, more tests will be needed for that.