Error loading command modules 'containerapp' and 'cdn' due to msrest import deadlock under Python 3.14 (pipx install) #32980
Description
Describe the bug
When running any az command (e.g. az login), two errors are printed to stderr on startup:
Error loading command module 'containerapp': 'msrest'
Error loading command module 'cdn': deadlock detected by _ModuleLock('msrest.http_logger') at <address>
Despite these errors, the affected commands (az containerapp, az cdn) still appear to load successfully and are usable. The errors are non-fatal but appear on every invocation.
Environment
| azure-cli version | 2.84.0 |
| Python version | 3.14.3 |
| Installation method | pipx |
| OS | macOS 15.7.4 (Sequoia), arm64 |
Steps to reproduce
- Install azure-cli via pipx on macOS arm64 with Python 3.14:
pipx install azure-cli - Run any az command:
az login
Expected behavior
No errors printed to stderr on startup. Command modules load silently.
Actual behavior
Two errors appear every invocation (address will vary):
Error loading command module 'containerapp': 'msrest'
Error loading command module 'cdn': deadlock detected by _ModuleLock('msrest.http_logger') at 4711984592
Root cause analysis
This appears to be a recurrence of the Python import-lock race condition fixed in PR #26287 (which addressed requests.models deadlocks in Python 3.10.10). The same multi-threaded command module loading in azure.cli.core triggers a _ModuleLock deadlock on msrest.http_logger when running under Python 3.14, and a KeyError: 'msrest' in the containerapp module (likely due to msrest being only partially initialized in one thread when another accesses it).
msrest is present and importable in the venv — single-threaded imports of both modules succeed without error. The failures are specific to the concurrent loading path.