test(scripting-piscine): improve py exercise tester

switch from py2 to py3
make pytest stop at first failure

sh/tests/Dockerfile

@@ -2,8 +2,8 @@ FROM docker.01-edu.org/debian:10.9-slim
 
 RUN apt-get update
 RUN apt-get -y install jq curl
-RUN apt-get -y install python-pip
-RUN pip install -U pytest
+RUN apt-get -y install python3-pip
+RUN pip3 install -U pytest
 
 WORKDIR /app/assets/superhero
 RUN curl --remote-name --location https://demo.01-edu.org/assets/superhero/all.json

sh/tests/entrypoint.sh

@@ -9,7 +9,7 @@ cd app
 if test -f "${EXERCISE}_test.sh"; then
 	bash "${EXERCISE}_test.sh"
 elif test -f "${EXERCISE}_test.py"; then
-	pytest "${EXERCISE}_test.py"
+	pytest -x "${EXERCISE}_test.py"
 else
 	echo "No test file found for the exercise : $EXERCISE"
 	exit 1