ReadDetectFileobjTest: repair Windows disasters by opening

the file object in binary mode.

The Windows buildbot slaves shouldn't swap themselves to death
anymore.  However, test_tarfile may still fail because of a
temp directory left behind from a previous failing run.
Windows buildbot owners may need to remove that directory
by hand.

Lib/test/test_tarfile.py

@@ -221,7 +221,8 @@ class ReadDetectFileobjTest(ReadTest):
 
     def setUp(self):
         name = tarname(self.comp)
-        self.tar = tarfile.open(name, mode=self.mode, fileobj=file(name))
+        self.tar = tarfile.open(name, mode=self.mode,
+                                fileobj=open(name, "rb"))
 
 class ReadAsteriskTest(ReadTest):