Description

Fixes #7478

Fusion: https://source.cloud.google.com/results/invocations/dd66b6e0-62fb-40c6-b05a-1301c18ebbbd/targets

Steps to re-create error:

Using appengine as an example, but should apply to other affected samples.

1. Use locally or cloud shell and navigate to the sample folder and simply install requirements

pip3 install -r requirements.txt
pip3 install -r requirements-test.txt

1. You should see the same error logs like so after executing the following:

python3 main.py

Error:

1. Verify this PR no longer produces those missing module errors and for appengine - verify the tests are passing locally.

Note: You'll see varying versions for markupsafe are being installed. This is due to the varying Flask versions per sample
ref: pallets/flask#4455 (comment)

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.6 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• Please merge this PR for me once it is approved.
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample