* [3.6] bpo-30822: Fix testing of datetime module. (GH-2530) (GH-2783)

Only C implementation was tested.
(cherry picked from commit 287c5594)

* [3.6] bpo-30822: Fix testing of datetime module. (GH-2530) (GH-2783)

Only C implementation was tested..
(cherry picked from commit 287c5594)