'Turn a list of usernames into user objects'

def _usernames_to_users(self, usernames):

    users = []
    for username in usernames:
        username = self.authenticator.normalize_username(username)
        user = self.find_user(username)
        if (user is None):
            raise web.HTTPError(400, ('No    such    user:    %s' % username))
        users.append(user.orm_user)
    return users
