[2.7] bpo-35133: Fix mistakes when concatenate string literals on different lines. (GH-10284) (GH-10335) (GH-10336)

Two kind of mistakes:

1. Missed space. After concatenating there is no space between words.

2. Missed comma. Causes unintentional concatenating in a list of strings.
(cherry picked from commit 34fd4c20)
(cherry picked from commit 7054e5c8)