ci: use prebuilt docker image in presubmits (GoogleCloudPlatform#9108)

* ci: use prebuilt docker image in presubmits * update lint session * Unset TRAMPOLINE_DOCKERFILE by default * Make a change to the Dockerfile to trigger all tests to run. --------- Co-authored-by: Karl Weinmeister <11586922+kweinmeister@users.noreply.github.com>

Author: parthea

.kokoro/docker/Dockerfile

@@ -156,7 +156,7 @@ RUN wget --no-check-certificate -O /tmp/get-pip.py 'https://bootstrap.pypa.io/ge
  # https://github.com/docker-library/python/pull/100
  && [ "$(pip list |tac|tac| awk -F '[ ()]+' '$1 == "pip" { print $2; exit }')" = "$PYTHON_PIP_VERSION" ]
 
-# Ensure Pip for all python3 versions
+# Ensure Pip for all python3 versions.
 RUN python3.9 /tmp/get-pip.py
 RUN python3.8 /tmp/get-pip.py
 RUN python3.7 /tmp/get-pip.py

.kokoro/lint/common.cfg

@@ -44,8 +44,3 @@ env_vars: {
  key: "RUN_TESTS_SESSION"
  value: "lint"
 }
-
-env_vars: {
- key: "TRAMPOLINE_DOCKERFILE"
- value: ".kokoro/docker/Dockerfile"
-}

.kokoro/python2.7/common.cfg

@@ -52,8 +52,3 @@ env_vars: {
  key: "BUILD_SPECIFIC_GCLOUD_PROJECT"
  value: "python-docs-samples-tests"
 }
-
-env_vars: {
- key: "TRAMPOLINE_DOCKERFILE"
- value: ".kokoro/docker/Dockerfile"
-}

.kokoro/python3.10/common.cfg

@@ -59,8 +59,3 @@ env_vars: {
  key: "NUM_TEST_WORKERS"
  value: "10"
 }
-
-env_vars: {
- key: "TRAMPOLINE_DOCKERFILE"
- value: ".kokoro/docker/Dockerfile"
-}

.kokoro/python3.7/common.cfg

@@ -59,8 +59,3 @@ env_vars: {
  key: "NUM_TEST_WORKERS"
  value: "10"
 }
-
-env_vars: {
- key: "TRAMPOLINE_DOCKERFILE"
- value: ".kokoro/docker/Dockerfile"
-}

.kokoro/python3.8/common.cfg

@@ -59,8 +59,3 @@ env_vars: {
  key: "NUM_TEST_WORKERS"
  value: "10"
 }
-
-env_vars: {
- key: "TRAMPOLINE_DOCKERFILE"
- value: ".kokoro/docker/Dockerfile"
-}

.kokoro/python3.9/common.cfg

@@ -59,8 +59,3 @@ env_vars: {
  key: "NUM_TEST_WORKERS"
  value: "10"
 }
-
-env_vars: {
- key: "TRAMPOLINE_DOCKERFILE"
- value: ".kokoro/docker/Dockerfile"
-}

.trampolinerc

@@ -47,7 +47,7 @@ if [[ -z "${TRAMPOLINE_IMAGE:-}" ]]; then
 fi
 
 if [[ -z "${TRAMPOLINE_DOCKERFILE:-}" ]]; then
- TRAMPOLINE_DOCKERFILE=".kokoro/docker/Dockerfile"
+ TRAMPOLINE_DOCKERFILE=""
 fi
 
 if [[ -z "${RUN_TESTS_SESSION:-}" ]]; then