[3.12] gh-114331: Skip decimal test_maxcontext_exact_arith on s390x (GH-117326) (#117327)

gh-114331: Skip decimal test_maxcontext_exact_arith on s390x (GH-117326)
(cherry picked from commit 6702d2b)

Co-authored-by: Victor Stinner <[email protected]>

Author: miss-islington

Lib/test/test_decimal.py

@@ -37,7 +37,8 @@
                           requires_legacy_unicode_capi, check_sanitizer)
 from test.support import (TestFailed,
                           run_with_locale, cpython_only,
-                          darwin_malloc_err_warning, is_emscripten)
+                          darwin_malloc_err_warning, is_emscripten,
+                          skip_on_s390x)
 from test.support.import_helper import import_fresh_module
 from test.support import threading_helper
 from test.support import warnings_helper
@@ -5654,6 +5655,9 @@ def __abs__(self):
     @unittest.skipIf(check_sanitizer(address=True, memory=True),
                      "ASAN/MSAN sanitizer defaults to crashing "
                      "instead of returning NULL for malloc failure.")
+    # gh-114331: The test allocates 784 271 641 GiB and mimalloc does not fail
+    # to allocate it when using mimalloc on s390x.
+    @skip_on_s390x
     def test_maxcontext_exact_arith(self):
 
         # Make sure that exact operations do not raise MemoryError due