[web2py] custom auth use email field instead of username

[selecta]

I have customized my auth table and allow via a configuration file to
login via LDAP. If LDAP is enabled the username field should be used
for login if LDAP is not enabled the email field should be used for
logging in.
Is this possible?
looking into def login_bare() and  def login() it seems like that when
a username field is available it is always used.
I guess I have to fix this on my own, right? Just checking to see if
am correct.