add python

Dockerfile

@@ -14,6 +14,8 @@ RUN \
   apt update && \
   apt install -y vim.tiny && \
   apt install -y python-cheetah && \
+  apt install -y python3 && \
+  pip install pyserial && \
   rm -rf /var/lib/apt/lists/* && \
   cd /tmp && \
   wget ${ArduinoDownloadUrl}/${ArduinoPackage} && \