Enable warnings as errors in custreamz (#15642)

Part of rapidsai/build-planning#26

Builds on #15634

Authors:
  - Matthew Roeschke (https://github.com/mroeschke)
  - GALI PREM SAGAR (https://github.com/galipremsagar)

Approvers:
  - Lawrence Mitchell (https://github.com/wence-)

URL: #15642

python/custreamz/pyproject.toml

@@ -103,3 +103,13 @@ skip = [
     "dist",
     "__init__.py",
 ]
+
+[tool.pytest.ini_options]
+filterwarnings = [
+    "error",
+    "ignore:unclosed <socket.socket:ResourceWarning",
+    "ignore:Port .* is already in use.:UserWarning:distributed",
+    # Should be fixed in the next streamz release
+    # https://github.com/python-streamz/streamz/commit/2812f1f961dfcb3f17e948d8b12a12472975558e
+    "ignore:pkg_resources is deprecated as an API:DeprecationWarning:streamz",
+]