fountain.ldap: Rework connection initialization

fountain/ldap.py

 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 import ssl
-from ldap3 import Server, Connection, RESTARTABLE
+from ldap3 import Server, Connection, RESTARTABLE, DSA
 from ldap3.core.tls import Tls
 from ldap3.utils.uri import parse_uri
 from django.conf import settings
@@ -29,11 +29,21 @@ class Ldap(object):
     
     @cached_property
     def connection(self):
+        server_kwargs = {
+            'host': self.LDAP_PARAMS['host'],
+            'use_ssl': False,
+            'port': self.LDAP_PARAMS['port']
+        }
         if self.LDAP_PARAMS['ssl']:
-            tls = Tls(ca_certs_file=self.LDAP_CA_CERT, validate=ssl.CERT_REQUIRED)
-            s=Server(self.LDAP_PARAMS['host'], use_ssl=True, tls=tls)
-        else:
-            s=Server(self.LDAP_PARAMS['host'], use_ssl=False)
+            server_kwargs['use_ssl'] = True
+            server_kwargs['tls'] = Tls(ca_certs_file=self.LDAP_CA_CERT, validate=ssl.CERT_REQUIRED)
+
+        # In case the LDAP server is the local host we assume a testing server.
+        # "SCHEMA" queries might not be available, so use "DSA" instead.      
+        if self.LDAP_PARAMS['host'] == 'localhost':
+            server_kwargs['get_info'] = DSA
+            
+        s=Server(**server_kwargs)
         c = Connection(
             s,
             auto_bind=True,