This should be treated as specific and technical terminology associated with a particular educations and examinations system, and not translated.
In a Resumé or CV you list your qualifications exactly as you received them "A diploma mention bien" And you may indicate by means of a footnote or endnote an equivalence with the local examination system "*equivalent to a diploma with high honours". You do this as a courtesy and convenience to the person receiving your CV.
Hiding the actual qualification behind a translation could cause you to be accused of misrepresenting your qualification and lead to difficult questions at interview.