def check_cmfcc(cls):
        """
        Check whether Python C extension ``cmfcc`` can be imported.

        Return ``True`` on failure and ``False`` on success.

        :rtype: bool
        """
        if gf.can_run_c_extension("cmfcc"):
            gf.print_success(u"aeneas.cmfcc   AVAILABLE")
            return False
        gf.print_warning(u"aeneas.cmfcc   NOT AVAILABLE")
        gf.print_info(u"  You can still run aeneas but it will be significantly slower")
        gf.print_info(u"  Please refer to the installation documentation for details")
        return True