Handle LDAP errors

fountain/ldap.py

 # -*- coding: utf-8 -*-
 from __future__ import unicode_literals
+import logging
 import ssl
 import ldap3
 from ldap3 import Server, Connection, SYNC, OFFLINE_SLAPD_2_4, MOCK_SYNC
@@ -11,7 +12,7 @@ from django.conf import settings
 from django.contrib.auth import get_user_model
 from django.utils.functional import cached_property
 
-DEFAULT_LDAP_TIMEOUT  = 3
+DEFAULT_LDAP_TIMEOUT = 3
 DEFAULT_LDAP_SYNC_URI = 'ldaps://ldap.tu-chemnitz.de/ou=Users,dc=tu-chemnitz,dc=de'
 
 DEFAULT_LDAP_SYNC_USER_ATTRIBUTES = {
@@ -20,6 +21,8 @@ DEFAULT_LDAP_SYNC_USER_ATTRIBUTES = {
     'mail': 'email',
 }
 
+logger = logging.getLogger(__name__)
+
 
 class Ldap(object):
     def __init__(self):
@@ -64,7 +67,7 @@ class Ldap(object):
                 server_kwargs['use_ssl'] = True
                 server_kwargs['tls'] = Tls(ca_certs_file=self.LDAP_CA_CERT, validate=ssl.CERT_REQUIRED)
                 
-            s=Server(**server_kwargs)        
+            s = Server(**server_kwargs)
             connection_kwargs = {
                 'server': s,
                 'auto_bind': True,
@@ -72,8 +75,11 @@ class Ldap(object):
                 'password': self.LDAP_SYNC_BASE_PASS,
                 'client_strategy': SYNC,
             }
-            
-            return Connection(**connection_kwargs)
+            try:
+                return Connection(**connection_kwargs)
+            except LDAPException:
+                logger.warning("LDAP connection failed, LDAP updates will not be available.")
+                return None
 
     def get_attributes(self, username):
         """
@@ -105,6 +111,8 @@ class Ldap(object):
         }
         
         conn = self.connection
+        if not conn:
+            return {}
         try:
             result = conn.search(**search_kwargs)
         except LDAPException: