Import the nested_scopes feature twice, to exercise the patch introduced

to avoid segfaults when more than one feature is named in the future
statement.

This tests for regression of SF bug #407394.

Lib/test/test_future1.py

 """This is a test"""
-from __future__ import nested_scopes
+
+# Import the name nested_scopes twice to trigger SF bug #407394 (regression).
+from __future__ import nested_scopes, nested_scopes
 
 def f(x):
     def g(y):