With a fresh install of Contao 4.9 LTS and the Contao-CalendarEditor extension installed, an error appears on top of the page where the "event editor" module is placed. There is in fact no such configuration file in the folder location and the name of the file was probably a test name during development.
Cannot find rich text editor configuration file ".../public_html/.../vendor/danielgausi/contao-calendareditor-bundle/src/Resources/contao/tinyMCE/wuppdi.php"