You can call me a pedant, but "сделать ошибку по-русски", as well as "ошибка по-[language name]" itself, sounds absolutely wrong to me.
You can "сделать ошибку, говоря по-русски". But "ошибка по-русски" sounds like "a mistake a là russe".
P.S. One can write "Поправляйте мои ошибки, когда я пишу по-русски".