old_email = b"old@mail.com"
new_email = b"new@mail.com"
new_name = "newname"

if commit.author_email == old_email:
    commit.author_name = new_name.encode("utf-8")
    commit.author_email = new_email
if commit.committer_email == old_email:
    commit.committer_name = new_name.encode("utf-8")
    commit.committer_email = new_email