install_aliases(): anticipate the absence of test.test_support on Py2 (issue #109)

This seems to be missing on some installations.

Author: edschofield

src/future/standard_library/__init__.py

@@ -482,8 +482,11 @@ def install_aliases():
         import test
     except ImportError:
         pass
-    else:
+    try:
         from future.moves.test import support
+    except ImportError:
+        pass
+    else:
         test.support = support
         sys.modules['test.support'] = support