Use db.close_old_connections instead of close_connection

Django 1.8 removed the `db.close_connection` method.

Thanks to Alfredo Armanini (@phingage) for the patch

Author: acdha

AUTHORS

@@ -100,3 +100,5 @@ Thanks to
     * Phill Tornroth (phill-tornroth) for several patches improving UnifiedIndex and ElasticSearch support
     * Philippe Luickx (philippeluickx) for documenting how to provide backend-specific facet options
     * Felipe Prenholato (@chronossc) for a patch making it easy to exclude documents from indexing using custom logic
+    * Alfredo Armanini (@phingage) for a patch fixing compatibility with database API changes in Django 1.8
+

haystack/management/commands/update_index.py

@@ -8,7 +8,12 @@
 from datetime import timedelta
 from optparse import make_option
 
-from django import db
+try:
+    from django.db import close_old_connections
+except ImportError:
+    # This can be removed when we drop support for Django 1.7 and earlier:
+    from django.db import close_connection as close_old_connections
+
 from django.core.management.base import LabelCommand
 from django.db import reset_queries
 
@@ -49,7 +54,7 @@ def worker(bits):
         # out connections (via ``... = {}``) destroys in-memory DBs.
         if 'sqlite3' not in info['ENGINE']:
             try:
-                db.close_connection()
+                close_old_connections()
                 if isinstance(connections._connections, dict):
                     del(connections._connections[alias])
                 else:
@@ -206,7 +211,7 @@ def update_backend(self, label, using):
                 # workers resetting connections leads to references to models / connections getting
                 # stale and having their connection disconnected from under them. Resetting before
                 # the loop continues and it accesses the ORM makes it better.
-                db.close_connection()
+                close_old_connections()
 
             qs = index.build_queryset(using=using, start_date=self.start_date,
                                       end_date=self.end_date)