tests: split systests out into separate Kokoro jobs (#516)

Closes #515

.github/sync-repo-settings.yaml

@@ -0,0 +1,11 @@
+# https://github.com/googleapis/repo-automation-bots/tree/master/packages/sync-repo-settings
+# Rules for master branch protection
+branchProtectionRules:
+# Identifies the protection rule pattern. Name of the branch to be protected.
+# Defaults to `master`
+- pattern: master
+  requiredStatusCheckContexts:
+    - 'Kokoro'
+    - 'cla/google'
+    - 'Kokoro system-2.7'
+    - 'Kokoro system-3.8'

.kokoro/presubmit/presubmit.cfg

@@ -1 +1,7 @@
-# Format: //devtools/kokoro/config/proto/build.proto
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Disable system tests.
+env_vars: {
+    key: "RUN_SYSTEM_TESTS"
+    value: "false"
+}

.kokoro/presubmit/system-2.7.cfg

@@ -0,0 +1,7 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Only run this nox session.
+env_vars: {
+    key: "NOX_SESSION"
+    value: "system-2.7"
+}

.kokoro/presubmit/system-3.8.cfg

@@ -0,0 +1,7 @@
+# Format: //devtools/kokoro/config/proto/build.proto
+
+# Only run this nox session.
+env_vars: {
+    key: "NOX_SESSION"
+    value: "system-3.8"
+}

owlbot.py

@@ -26,6 +26,7 @@
 # ----------------------------------------------------------------------------
 templated_files = common.py_library(
     cov_level=100,
+    split_system_tests=True,
     system_test_external_dependencies=[
         "google-cloud-iam",
         "google-cloud-pubsub < 2.0.0",
@@ -38,7 +39,11 @@
 )
 
 s.move(
-    templated_files, excludes=["docs/multiprocessing.rst", "noxfile.py", "CONTRIBUTING.rst"],
+    templated_files, excludes=[
+        "docs/multiprocessing.rst",
+        "noxfile.py",
+        "CONTRIBUTING.rst",
+    ],
 )
 
 s.shell.run(["nox", "-s", "blacken"], hide_output=False)