If the bind_dn and bind_password are not specified the behavior is supposed to be an anonymous bind which is fine for most attribute lookups. The code in infoldap at line 108 does this:

    conn.simple_bind_s(self.bind_dn, self.bind_password)

where self.bind_dn and self.bind_password are both None, but this won't work for an anonymous bind. The documented way to perform an anonymous bind with python-lap is to not pass any parameters to simple_bind_s(). It's bad API design on the part of python-ldap, it should accept None, but it doesn't.

The code should probably look something like this:

if self.bind_dn is None and self.bind_password is None:
    conn.simple_bind_s()
else:
    conn.simple_bind_s(self.bind_dn, self.bind_password)