The 'moodle-plugin-ci savepoints' plugin on Travis fails when the version is a string (as demonstrated on https://travis-ci.org/github/gjb2048/moodle-format_grid/jobs/743585346#L601-L609) and yet the specification of the function allows this -> https://github.com/moodle/moodle/blob/MOODLE_310_STABLE/lib/upgradelib.php#L365.

My fix was: https://github.com/gjb2048/moodle-format_grid/commit/90e4e14560b3e72cc0a6a90e167adc552c7c30a3#diff-fcb317575e9e6245fdf1590e51a86685b61c2cc9573a9df8034323ccb3ef614f resulting in https://travis-ci.org/github/gjb2048/moodle-format_grid/jobs/743588155#L592-L596.