I think the best context for the build_test_suite change is probably to look at the end of https://code.launchpad.net/~cjwatson/launchpad/code-doctests-future-imports/+merge/345470. Briefly, for doctests we can't just do "from __future__ import print_function" etc. at the top of the file; instead, we have to do a much more awkward construction of inserting print_function etc. into their globals when constructing the corresponding test suite. lp.testing.systemdocs.setUp(future=True) is a way of spelling that without having to incur too much verbiage at every site.
I think the best context for the build_test_suite change is probably to look at the end of https:/ /code.launchpad .net/~cjwatson/ launchpad/ code-doctests- future- imports/ +merge/ 345470. Briefly, for doctests we can't just do "from __future__ import print_function" etc. at the top of the file; instead, we have to do a much more awkward construction of inserting print_function etc. into their globals when constructing the corresponding test suite. lp.testing. systemdocs. setUp(future= True) is a way of spelling that without having to incur too much verbiage at every site.