Add jsonschema python package to the dockerfile.

Dockerfile

@@ -98,7 +98,7 @@ RUN set -x -e; \
     apt-get -y install --no-install-recommends python3-distutils protobuf-compiler; \
     wget -q https://bootstrap.pypa.io/pip/3.6/get-pip.py; \
     python3 get-pip.py; \
-    pip3 install dataclasses Jinja2 protobuf pytest xmlschema lxml; \
+    pip3 install dataclasses Jinja2 protobuf pytest xmlschema lxml jsonschema; \
     rm -rf get-pip.py /var/lib/apt/lists/*
 
 # Python 3.8
@@ -108,7 +108,7 @@ RUN set -x -e; \
     apt-get -y install --no-install-recommends python3.8 python3.8-distutils; \
     wget -q https://bootstrap.pypa.io/get-pip.py; \
     python3.8 get-pip.py; \
-    python3.8 -m pip install dataclasses Jinja2 protobuf pytest xmlschema lxml; \
+    python3.8 -m pip install dataclasses Jinja2 protobuf pytest xmlschema lxml jsonschema; \
     rm -rf get-pip.py /var/lib/apt/lists/*
 
 COPY entrypoint.py /usr/local/bin/entrypoint