Fix a place where it's pretty clear that a binary open mode was intended.

(The new I/O library revealed the problem.)

Lib/test/test_bz2.py

@@ -243,7 +243,7 @@ class BZ2FileTest(BaseTest):
         self.createTempFile()
         bz2f = BZ2File(self.filename, "U")
         bz2f.close()
-        f = open(self.filename)
+        f = open(self.filename, "rb")
         f.seek(0, 2)
         self.assertEqual(f.tell(), len(self.DATA))
         f.close()