test: update the ci/cd pipeline (#794)

* test: update the ci/cd pipeline

* remove reference to cover and clean up linting error

* Update noxfile.py

* define sessions that run during presubmit

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* updates owlbot to avoid overwriting presubmit.cfg

* restores file changes that owlbot took out

* updates session name

---------

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

Author: chalmerlowe

.kokoro/presubmit/presubmit.cfg

@@ -1 +1,7 @@
-# Format: //devtools/kokoro/config/proto/build.proto
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Only run the following session(s)
+env_vars: {
+  key: "NOX_SESSION"
+  value: "blacken lint lint_setup_py docs"
+}

noxfile.py

@@ -98,9 +98,6 @@ def wrapper(*args, **kwargs):
 
 # 'docfx' is excluded since it only needs to run in 'docs-presubmit'
 nox.options.sessions = [
-    "unit",
-    "system",
-    "cover",
     "lint",
     "lint_setup_py",
     "blacken",

owlbot.py

@@ -58,6 +58,7 @@
         "README.rst",
         # exclude this file as we have an alternate prerelease.cfg
         ".kokoro/presubmit/prerelease-deps.cfg",
+        ".kokoro/presubmit/presubmit.cfg",
     ],
 )