Update python env var in ubuntu image.

Dockerfile

@@ -1,14 +1,16 @@
 FROM ubuntu:focal
 ENV LANG C.UTF-8
 ENV DEBIAN_FRONTEND noninteractive
-ENV PYTHONPATH "/usr/lib/python3.6/:/usr/local/lib/python3.6/dist-packages/:/work:/work/banhammer:/work/hmt-servers"
 ENV PYTHONUNBUFFERED True
 
 WORKDIR /work
+
 RUN apt-get update -y && \
     apt-get install -y automake bash black build-essential curl git jq libffi-dev libgmp-dev libtool mypy nodejs npm \
 	pandoc pkg-config python3-boto python3-dev python3-pip libsnappy-dev
 
+ENV PYTHONPATH "/usr/lib/python3.8/:/usr/local/lib/python3.8/dist-packages/:/work:/work/banhammer:/work/hmt-servers"
+
 COPY package.json /work/
 RUN npm install