chore: migrate to owl bot (#270)

* chore: migrate to owl bot

* chore: copy files from googleapis-gen 130ce904e5d546c312943d10f48799590f9c0f66

* chore: run the post processor

* 🦉 Updates from OwlBot

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: parthea

logging/samples/snippets/noxfile.py

@@ -172,10 +172,16 @@ def blacken(session: nox.sessions.Session) -> None:
 def _session_tests(session: nox.sessions.Session, post_install: Callable = None) -> None:
     """Runs py.test for a particular project."""
     if os.path.exists("requirements.txt"):
-        session.install("-r", "requirements.txt")
+        if os.path.exists("constraints.txt"):
+            session.install("-r", "requirements.txt", "-c", "constraints.txt")
+        else:
+            session.install("-r", "requirements.txt")
 
     if os.path.exists("requirements-test.txt"):
-        session.install("-r", "requirements-test.txt")
+        if os.path.exists("constraints-test.txt"):
+            session.install("-r", "requirements-test.txt", "-c", "constraints-test.txt")
+        else:
+            session.install("-r", "requirements-test.txt")
 
     if INSTALL_LIBRARY_FROM_SOURCE:
         session.install("-e", _get_repo_root())