Issue #7449, part 4: skip test_multiprocessing if thread support is disabled

import threading after _multiprocessing to raise a more revelant error message:
"No module named _multiprocessing". _multiprocessing is not compiled without
thread support.
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index 8f32cfb..03629d1 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -5,7 +5,6 @@
 #
 
 import unittest
-import threading
 import Queue
 import time
 import sys
@@ -18,9 +17,11 @@
 import logging
 from test import test_support
 from StringIO import StringIO
-
-
 _multiprocessing = test_support.import_module('_multiprocessing')
+# import threading after _multiprocessing to raise a more revelant error
+# message: "No module named _multiprocessing". _multiprocessing is not compiled
+# without thread support.
+import threading
 
 # Work around broken sem_open implementations
 test_support.import_module('multiprocessing.synchronize')