title: Google Cloud Build can't find Python venv... For Java Spring Boot project
body: <p>I have a usual Java 11 Spring Boot application that is deployed to Heroku at the moment.</p>
  <p>I can deploy the app manually to AppEngine via a local call to <code>gcloud app deploy</code></p>
  <p>However, I'm struggling for about 2 hours to make the Google Cloud Build to build and deploy the application automatically. It crashes not being able to find python, but I have absolutely no idea why does it try to look for the python anyway.</p>
  <p>Here is the <code>cloubuild.yaml</code>:</p>
  <pre><code>  - name: maven:3.6.3-adoptopenjdk-11
      entrypoint: mvn
      args: ['--version']
  
    - name: maven:3.6.3-adoptopenjdk-11
      entrypoint: mvn
      args: ['package']
  
    - name: 'gcr.io/cloud-builders/gcloud'
      args: ['app', 'deploy', 'app.yaml']
  </code></pre>
  <p>Here is the app yaml in the same root folder:</p>
  <pre><code>runtime: java11
  env: standard
  instance_class: F2
  automatic_scaling:
    max_instances: 1
  </code></pre>
  <p>Here is the error part of the output:</p>
  <pre><code>Step #2: descriptor:      [/workspace/app.yaml]
  Step #2: source:          [/workspace]
  Step #2: target project:  [atomic-parity-282520]
  Step #2: target service:  [default]
  Step #2: target version:  [20200711t113051]
  Step #2: target url:      [https://atomic-parity-282520.ew.r.appspot.com]
  Step #2: 
  Step #2: 
  Step #2: Do you want to continue (Y/n)?  
  Step #2: Beginning deployment of service [default]...
  Step #2: Created .gcloudignore file. See `gcloud topic gcloudignore` for details.
  Step #2: ERROR: gcloud crashed (OSError): [Errno 2] No such file or directory: '/workspace/venv/bin/python3'
  Step #2: 
  Step #2: If you would like to report this issue, please run the following command:
  Step #2:   gcloud feedback
  Step #2: 
  Step #2: To check gcloud for common problems, please run the following command:
  Step #2:   gcloud info --run-diagnostics
  Finished Step #2
  ERROR
  ERROR: build step 2 &quot;gcr.io/cloud-builders/gcloud&quot; failed: step exited with non-zero status: 1
  </code></pre>