Hello,
This is probably a bias of Python when it scans the Fortran to decide what subroutines must be compiled and in which order. If nothing in the libraries calls your module it will not be compiled. A way to prove this would consist in putting your module in the Fortran file of your specific case. There it would be compiled and you could see if it works. If it solves the problem a workaround solution would consist in adding the name of your module manually in the *.cmdf files which are in the Fortran libraries, e.g. telemac2d.cmdf, where you can find lists of subroutines to be compiled. However if you manually add a subroutine you must not rescan after, lest it would erase your modfication.
I hope these hints are helpful and not wrong, I cannot check on a Telemac installation where I am.
With best regards,
Jean-Michel Hervouet