os.sendfile() test: fix "AttributeError: 'NoneType' object has no attribute 'Thread'" when running tests with --without-threads option. reference: http://bugs.python.org/issue10882#msg136257
os.sendfile() test: fix "AttributeError: 'NoneType' object has no attribute 'Thread'" when running tests with --without-threads option.
reference: http://bugs.python.org/issue10882#msg136257

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator