fix: intermittent _DeadlockError

Author: necusjz

src/azure-cli-core/azure/cli/core/aaz/_poller.py

@@ -62,6 +62,10 @@ def __init__(self, polling_generator, result_callback):
         self._done = None
         self._exception = None
 
+        # MSAL lazily imports requests when the credential is created on the polling thread,
+        # which can raise _DeadlockError (seen on Python 3.14). Import it here on the main thread first.
+        import requests  # pylint: disable=unused-import
+
         self._done = threading.Event()
         self._thread = threading.Thread(
             target=with_current_context(self._start),

src/azure-cli-core/azure/cli/core/tests/test_aaz_poller.py

@@ -0,0 +1,30 @@
+# --------------------------------------------------------------------------------------------
+# Copyright (c) Microsoft Corporation. All rights reserved.
+# Licensed under the MIT License. See License.txt in the project root for license information.
+# --------------------------------------------------------------------------------------------
+import sys
+import unittest
+from unittest import mock
+
+from azure.cli.core.aaz._poller import AAZLROPoller
+
+
+class TestAAZLROPoller(unittest.TestCase):
+
+    def test_requests_imported_before_polling_thread(self):
+        loaded = []
+
+        def polling_generator():
+            loaded.append("requests" in sys.modules)
+            yield from ()
+
+        with mock.patch.dict(sys.modules):
+            for name in [n for n in sys.modules if n == "requests" or n.startswith("requests.")]:
+                del sys.modules[name]
+            AAZLROPoller(polling_generator=polling_generator(), result_callback=None).wait()
+
+        self.assertEqual(loaded, [True])
+
+
+if __name__ == "__main__":
+    unittest.main()