multiple index tests: correct handling of Whoosh teardown

We can't remove the Whoosh directory per-test - only after every
test has run…

tests/multipleindex/tests.py

@@ -1,3 +1,4 @@
+import os
 import shutil
 from django.conf import settings
 from django.test import TestCase
@@ -8,6 +9,15 @@
 from multipleindex.search_indexes import FooIndex
 from multipleindex.models import Foo, Bar
 
+def tearDownModule():
+    # Because Whoosh doesn't clean up its mess.
+    for name, opts in settings.HAYSTACK_CONNECTIONS.items():
+        if "WhooshEngine" not in opts['ENGINE']:
+            continue
+        p = opts['PATH']
+        if os.path.exists(p):
+            shutil.rmtree(p)
+
 
 class MultipleIndexTestCase(TestCase):
     def setUp(self):
@@ -46,8 +56,7 @@ def setUp(self):
     def tearDown(self):
         self.fi.clear()
         self.bi.clear()
-        # Because Whoosh doesn't clean up its mess.
-        shutil.rmtree(settings.HAYSTACK_CONNECTIONS['whoosh']['PATH'])
+
         super(MultipleIndexTestCase, self).setUp()
 
     def test_index_update_object_using(self):