downgrade 3.9.0 to 3.6.12 because threading issue

Change-Id: Ifaafd67c3b0b936c6aec1b916946130ea137ae66

python3/Dockerfile

@@ -8,8 +8,8 @@ FROM ubuntu:18.04
 MAINTAINER xt
 
 COPY sources.list /etc/apt/sources.list
-COPY Python-3.9.0.tar.xz ./python.tar.xz
-COPY Python-3.9.0.tar.xz.asc ./python.tar.xz.asc
+COPY Python-3.6.12.tar.xz ./python.tar.xz
+COPY Python-3.6.12.tar.xz.asc ./python.tar.xz.asc
 COPY get-pip.py ./get-pip.py
 
 # ensure local python is preferred over distribution python
@@ -43,7 +43,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
 	&& rm -rf /var/lib/apt/lists/*
 
 ENV GPG_KEY 0D96DF4D4110E5C43FBFB17F2D347EA6AA65421D
-ENV PYTHON_VERSION 3.9.0
+ENV PYTHON_VERSION 3.6.12
 
 RUN set -ex \
 	\
@@ -85,7 +85,7 @@ RUN cd /usr/local/bin \
 	&& ln -s python3-config python-config
 
 # if this is called "PIP_VERSION", pip explodes with "ValueError: invalid truth value '<VERSION>'"
-ENV PYTHON_PIP_VERSION 20.2.4
+ENV PYTHON_PIP_VERSION 18.0
 
 RUN set -ex; \
 	python get-pip.py \

python3/Python-3.6.12.tar.xz.asc

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