build(python): exit with success status if no samples found (#234)

Source-Link: googleapis/synthtool@53ea389
Post-Processor: gcr.io/repo-automation-bots/owlbot-python:latest@sha256:e1793a23ae0ee9aafb2e3a53b564a351f74790dbe3c2d75f8fc3b8c43e5c036c

Author: gcf-owl-bot[bot]

bigquery_storage/to_dataframe/noxfile.py

@@ -226,7 +226,7 @@ def py(session: nox.sessions.Session) -> None:
 
 
 def _get_repo_root() -> Optional[str]:
-    """Returns the root folder of the project."""
+    """ Returns the root folder of the project. """
     # Get root of this repository. Assume we don't have directories nested deeper than 10 items.
     p = Path(os.getcwd())
     for i in range(10):