gh-157415: Skip @support.nomemtest if Python is built with TSAN

There is a known data race involving PyMem_SetAllocator(). Just skip
tests using _testcapi.set_nomemory() is Python is built with the
thread sanitizer.

Mark test_io.test_memoryio test using _testcapi.set_nomemory()
with @support.nomemtest.

Author: vstinner

Lib/test/support/__init__.py

@@ -1373,7 +1373,11 @@ def internal(*args, **kwargs):
         import_module('_testcapi')
         return test(*args, **kwargs)
 
-    return cpython_only(internal)
+    use_tsan = check_sanitizer(thread=True)
+    reason ='not working with thread sanitizer (gh-157415)'
+    skip_if_tsan = unittest.skipIf(use_tsan, reason)
+
+    return cpython_only(skip_if_tsan(internal))
 
 def bigaddrspacetest(f):
     """Decorator for tests that fill the address space."""

Lib/test/test_io/test_memoryio.py

@@ -754,6 +754,7 @@ def __buffer__(self, flags):
         self.assertEqual(memio.getvalue(), b"01AAA56789")
         self.assertEqual(memio.tell(), 5)
 
+    @support.nomemtest
     def test_memory_error(self):
         # gh-157242: io.BytesIO() must not close the file on MemoryError
         _testcapi = import_helper.import_module('_testcapi')