texte = "Il était une fois"

voyelles = set(["a","e","i","o","u","y","é","è","ê","ë","à","ü","ö"])

texte_sans_voyelles = ""
for c in texte:
    minus = c.lower()
    if minus in voyelles:
        texte_sans_voyelles += "*"
    else:
        texte_sans_voyelles += c

print(texte_sans_voyelles)