ldap: Add workaround for ldap3 issue #177

This fixes Python3 compatibility

fountain/ldap.py

@@ -33,7 +33,7 @@ class Ldap(object):
     def get_attributes(self, username):
         conn = self.connection
         model_attrs = {}
-        if conn.search(self.LDAP_PARAMS['base'], '(uid=%s)' %username, attributes=self.LDAP_SYNC_USER_ATTRIBUTES.keys()):
+        if conn.search(self.LDAP_PARAMS['base'], '(uid=%s)' %username, attributes=tuple(self.LDAP_SYNC_USER_ATTRIBUTES)):
             for attr in self.LDAP_SYNC_USER_ATTRIBUTES:
                 if attr in conn.response[0]['attributes']:
                     model_attrs[self.LDAP_SYNC_USER_ATTRIBUTES[attr]] = conn.response[0]['attributes'][attr][0]