Fix Windows buildbot failures after r66469.
diff --git a/Lib/test/test_tempfile.py b/Lib/test/test_tempfile.py
index 0e5cb0f..0ef0925 100644
--- a/Lib/test/test_tempfile.py
+++ b/Lib/test/test_tempfile.py
@@ -314,7 +314,7 @@
         if not has_textmode:
             return            # ugh, can't use TestSkipped.
 
-        self.do_create(bin=0).write("blat\n")
+        self.do_create(bin=0).write(b"blat\n")
         # XXX should test that the file really is a text file
 
 test_classes.append(test__mkstemp_inner)