PYTHON-5837 Add beta Python 3.15 (#2840)

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: aclark4life

.github/workflows/test-python.yml

@@ -59,10 +59,10 @@ jobs:
       matrix:
         # Tests currently only pass on ubuntu on GitHub Actions.
         os: [ubuntu-latest]
-        python-version: ["3.10", "pypy-3.11", "3.13t"]
+        python-version: ["3.10", "pypy-3.11", "3.13t", "3.15"]
         mongodb-version: ["8.0"]
 
-    name: CPython ${{ matrix.python-version }}-${{ matrix.os }}
+    name: Python ${{ matrix.python-version }}-${{ matrix.os }}
     steps:
       - uses: actions/checkout@v6.0.2
         with:

test/test_fork.py

@@ -36,6 +36,10 @@
     is_greenthread_patched(),
     "gevent does not support POSIX-style forking.",
 )
+@unittest.skipIf(
+    sys.version_info >= (3, 15),
+    "fork() in multi-threaded processes is deprecated in Python 3.15+ (PYTHON-5874)",
+)
 class TestFork(IntegrationTest):
     def test_lock_client(self):
         # Forks the client with some items locked.