[3.13] gh-130293: Ensure test__colorize will pass on dumb terminals. (GH-130333) (#130334)

Ensure colorize tests will run on dumb terminals (or environment with TERM=dumb set)

(cherry picked from commit 1b070060c025a00d43566a6df65aa7631861d7af)

Co-authored-by: Russell Keith-Magee <russell@keith-magee.com>