Fix deprecation warning (#1801)
Fix deprecation warning (#1801)

logging.warn -> logging.warning to fix "DeprecationWarning: The 'warn' function is deprecated, use 'warning' instead"
GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples,GoogleCloudPlatform/python-docs-samples