When zlib can't be imported, zipfile raises RuntimeError, which causes
the test to be marked as failing rather than skipped.  Add an explicit
"import zlib" to prevent this.
diff --git a/Lib/test/test_zipfile.py b/Lib/test/test_zipfile.py
index bf7770b..87e99ec 100644
--- a/Lib/test/test_zipfile.py
+++ b/Lib/test/test_zipfile.py
@@ -1,3 +1,4 @@
+import zlib # implied prerequisite
 import zipfile, os, StringIO, tempfile
 from test_support import TestFailed