[3.7] bpo-40807: Show warnings once from codeop._maybe_compile (GH-20486) by miss-islington · Pull Request #20673 · python/cpython

With the test.support change backported, the new test runs on 3.7 and fails on
self.assertEqual(len(w.warnings), 1) because '0 is 0' does not cause SyntaxWarning in 3.7. I believe the same might be true of '\e' and DeprecationWarning. We could make the test pass by changing 1 to 0, but that would be equivalent to deleting the test, and the blurb would still be wrong.

I think we should hold off on this until we learn of code that will make the current test (and blurb) relevant, or until we are sure that there is no such code, or until the next and final 3.7 bugfix release (in about a month).