fix: suppress Python 3.14 deprecation warnings for asyncio policy API (#3129)

[r266-tech]

Description

Fixes #3129

Python 3.14 deprecates asyncio.get_event_loop_policy() and asyncio.set_event_loop_policy() with DeprecationWarning. These APIs are still the recommended way to configure uvloop and Windows event loop policies, so the fix wraps calls in warnings.catch_warnings() on Python >= 3.14 to suppress warnings originating from the asyncio module.

Changes

• sanic/server/loop.py: Wrapped event loop policy checks in warnings.catch_warnings() blocks for both try_use_uvloop() and try_windows_loop() functions

Testing

On Python 3.14, running Sanic with uvloop should no longer emit:

DeprecationWarning: 'asyncio.get_event_loop_policy' is deprecated and slated for removal in Python 3.16
DeprecationWarning: 'asyncio.set_event_loop_policy' is deprecated and slated for removal in Python 3.16

The pattern is intentionally kept simple — once Python 3.16 provides a loop_factory API, the warnings.catch_warnings wrapper can be replaced with direct set_event_loop_factory() calls.

[codecov]

Codecov Report

❌ Patch coverage is 46.15385% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.722%. Comparing base (5ffc7b3) to head (4cdeaaf).

Files with missing lines	Patch %	Lines
sanic/server/loop.py	46.153%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##              main     #3146       +/-   ##
=============================================
- Coverage   87.769%   87.722%   -0.048%     
=============================================
  Files          105       105               
  Lines         8152      8161        +9     
  Branches      1291      1293        +2     
=============================================
+ Hits          7155      7159        +4     
- Misses         692       696        +4     
- Partials       305       306        +1     

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[themavik]

module=asyncio in warnings.filterwarnings hides every DeprecationWarning from asyncio inside try_use_uvloop and try_windows_loop, not only the policy call. nit: narrow with message= if tests still pass.

[r266-tech]

Good catch, thanks. The filter is now narrowed to message= so it only matches the policy-API deprecation messages (get/set_event_loop_policy and the *EventLoopPolicy class aliases) instead of every DeprecationWarning raised from asyncio.

Verified on CPython 3.14.4: the policy warnings are suppressed — including asyncio.AbstractEventLoopPolicy, which uvloop's policy instantiation touches — while unrelated asyncio deprecations (e.g. asyncio.iscoroutinefunction) still surface. tests/test_server_loop.py passes.

Also rebased onto current main: the earlier red CI came from a bandit-baseline mismatch in the security env (pre-existing B105 findings unrelated to this diff), which is resolved on main now.