chore: fail samples nox session if python version is missing (#1546)

diff --git a/.github/.OwlBot.lock.yaml b/.github/.OwlBot.lock.yaml
index 2567653..ae6c57f 100644
--- a/.github/.OwlBot.lock.yaml
+++ b/.github/.OwlBot.lock.yaml
@@ -1,3 +1,3 @@
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:87eee22d276554e4e52863ec9b1cb6a7245815dfae20439712bf644348215a5a
+  digest: sha256:82b12321da4446a73cb11bcb6812fbec8c105abda3946d46e6394e5fbfb64c0f
diff --git a/samples/compute/noxfile.py b/samples/compute/noxfile.py
index b008613..1fd8956 100644
--- a/samples/compute/noxfile.py
+++ b/samples/compute/noxfile.py
@@ -98,6 +98,10 @@
     "True",
     "true",
 )
+
+# Error if a python version is missing
+nox.options.error_on_missing_interpreters = True
+
 #
 # Style Checks
 #