[3.11] gh-103606: Improve error message from logging.config.FileConfig (GH-103628) (#104687)

* gh-103606: Improve error message from logging.config.FileConfig (GH-103628)

(cherry picked from commit 152227b569c3a9b87fe0483706f704762ced6d75)

plus backport the followup exception change fix to that in #104701
3 files changed