skip two test_zlib tests failing on s390x

Code is originally from gh#python/cpython!31096, it was released
upstream in 3.11.0.

Fixes: gh#python#90781
Fixes: bpo-46623
Patch: bpo-46623-skip-zlib-s390x.patch

Lib/test/test_zlib.py

@@ -1,6 +1,7 @@
 import unittest
 from test import support
 import binascii
+import os
 import pickle
 import random
 import sys
@@ -15,6 +16,37 @@
         hasattr(zlib.decompressobj(), "copy"),
         'requires Decompress.copy()')
 
+# bpo-46623: On s390x, when a hardware accelerator is used, using different
+# ways to compress data with zlib can produce different compressed data.
+# Simplified test_pair() code:
+#
+#   def func1(data):
+#       return zlib.compress(data)
+#
+#   def func2(data)
+#       co = zlib.compressobj()
+#       x1 = co.compress(data)
+#       x2 = co.flush()
+#       return x1 + x2
+#
+# On s390x if zlib uses a hardware accelerator, func1() creates a single
+# "final" compressed block whereas func2() produces 3 compressed blocks (the
+# last one is a final block). On other platforms with no accelerator, func1()
+# and func2() produce the same compressed data made of a single (final)
+# compressed block.
+#
+# Only the compressed data is different, the decompression returns the original
+# data:
+#
+#   zlib.decompress(func1(data)) == zlib.decompress(func2(data)) == data
+#
+# Make the assumption that s390x always has an accelerator to simplify the skip
+# condition. Windows doesn't have os.uname() but it doesn't support s390x.
+skip_on_s390x = unittest.skipIf(
+    hasattr(os, 'uname') and
+    os.uname().machine in ['s390x', 's390'],
+    'skipped on s390x')
+
 
 class VersionTestCase(unittest.TestCase):
 
@@ -174,6 +206,7 @@ def test_keywords(self):
                                          bufsize=zlib.DEF_BUF_SIZE),
                          HAMLET_SCENE)
 
+    @skip_on_s390x
     def test_speech128(self):
         # compress more data
         data = HAMLET_SCENE * 128
@@ -225,6 +258,7 @@ def test_64bit_compress(self, size):
 
 class CompressObjectTestCase(BaseCompressTestCase, unittest.TestCase):
     # Test compression object
+    @skip_on_s390x
     def test_pair(self):
         # straightforward compress/decompress objects
         datasrc = HAMLET_SCENE * 128

Misc/NEWS.d/next/Tests/2022-02-03-09-45-26.bpo-46623.vxzuhV.rst

@@ -0,0 +1,2 @@
+Skip test_pair() and test_speech128() of test_zlib on s390x since they fail
+if zlib uses the s390x hardware accelerator. Patch by Victor Stinner.