support/testing/tests/package/test_python_flask: new test

This commit adds a test for python-flask package. As we are about to
add python-flask-expects-json together with a test, it made sense to
also add a test for python-flask itself.

As far as the DEVELOPERS file is concerned, the test files are added
both to the existing maintainer of package/python-flask, as well as to
myself.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

support/testing/tests/package/sample_python_flask.py

@@ -0,0 +1,7 @@
+from flask import Flask
+app = Flask(__name__)
+
+
+@app.route('/')
+def hello_world():
+    return 'Hello, World!'