def email_for_user(username, check_exists=True):
    """Return email for a user.

    Currently, just appends @ocf.berkeley.edu, but could eventually do
    something more complicated.
    """
    if check_exists:
        from ocflib.account.search import user_exists
        if not user_exists(username):
            raise ValueError('Account "{}" does not exist.'.format(username))
    return '{}@ocf.berkeley.edu'.format(username)
