chore: Catch DeprecationWarning of sphinx in running pytest

tests/conftest.py

@@ -1,12 +1,26 @@
 """Configuration for pytest."""
+import inspect
+
 import pytest
+from _pytest.config import Config
+from sphinx import deprecation
 from sphinx.testing.path import path
 
 pytest_plugins = "sphinx.testing.fixtures"
-
 collect_ignore = ["roots"]
 
 
+def pytest_configure(config: Config):  # noqa
+    for name, klass in inspect.getmembers(deprecation, inspect.isclass):
+        if not issubclass(klass, DeprecationWarning) and not issubclass(
+            klass, PendingDeprecationWarning
+        ):
+            continue
+        config.addinivalue_line(
+            "filterwarnings", f"error::{klass.__module__}.{klass.__name__}"
+        )
+
+
 @pytest.fixture(scope="session")
 def rootdir():
     """Set root directory to use testing sphinx project."""