tests: add testing for Python 3.15 (#17962)

Python 3.15 testing was skipped in a subset of packages. The follow up
work is tracked in
googleapis/google-cloud-python#17741

GitOrigin-RevId: 89cfe8573ddf99c0fc9ef1c98615d1769e561e4e
Change-Id: If5e17f4979e99f9f837ff86b04816ce87ad1fc7c

Author: parthea

noxfile.py

@@ -60,7 +60,7 @@
 
 DEFAULT_PYTHON_VERSION = "3.14"
 
-ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14"]
+ALL_PYTHON = ["3.10", "3.11", "3.12", "3.13", "3.14", "3.15"]
 UNIT_TEST_STANDARD_DEPENDENCIES = [
     "mock",
     PYTEST_VERSION,
@@ -283,6 +283,10 @@ def run_unit(session, install_test_extra):
 @nox.session(python=ALL_PYTHON)
 @nox.parametrize("test_extra", [True, False])
 def unit(session, test_extra):
+    if session.python == "3.15":
+        session.skip(
+            "Skipping 3.15 until wheels are available for pyarrow. Also pyproj wheels are needed for dependency geopandas."
+        )
     if test_extra:
         run_unit(session, install_test_extra=test_extra)
     else: