Fix pytest 3.3 failures

tests/server/test_storage.py

@@ -1,4 +1,3 @@
-import gc
 import pytest
 import os
 
@@ -24,9 +23,7 @@ def db(tmpdir, request):
     db = db_class(request.param)("db", False)
     yield db
     os.chdir(cwd)
-    # Make sure all the locks and handles are closed
-    del db
-    gc.collect()
+    db.close()
 
 
 def test_put_get(db):