Adding install_python_versions from Stocker

Modified the Stocker multi-python Dockerfile to enable it to be
installed on multiple systems, removed Python 2.7 which is apparently
now broken, and added Python 3.8 which has now been released.

install_python_versions.sh

+#!/usr/bin/env bash
+
+declare -a py_versions=( \
+      "2" \
+      "3" \
+      "3.5" \
+      "3.6" \
+      "3.7" \
+      "3.8" \
+    )
+
+if [ -f /etc/os-release ]; then
+  source /etc/os-release
+fi
+
+if which apt > /dev/null; then
+  apt update -qq
+  apt -y install \
+    make \
+    build-essential \
+    libssl-dev \
+    zlib1g-dev \
+    libbz2-dev \
+    libreadline-dev \
+    libsqlite3-dev \
+    wget \
+    curl \
+    llvm \
+    libncurses5-dev \
+    libncursesw5-dev \
+    xz-utils \
+    tk-dev \
+    libffi-dev \
+    liblzma-dev \
+    python-openssl \
+    git \
+    graphviz \
+    libxslt1-dev
+fi
+
+if which yum > /dev/null; then
+  yum -y groupinstall "Development Tools"
+  yum -y install \
+    bzip2 \
+    bzip2-devel \
+    git \
+    graphviz \
+    libffi-devel \
+    libxslt-devel \
+    openldap-devel \
+    openssl-devel \
+    readline-devel \
+    sqlite \
+    sqlite-devel \
+    xz \
+    xz-devel \
+    zlib-devel
+fi
+
+if [ ! -d ${HOME}/.pyenv ]; then
+  git clone https://github.com/pyenv/pyenv.git ${HOME}/.pyenv
+fi
+
+cd ${HOME}/.pyenv
+git pull
+cd ~-
+
+if [ ! -f ${HOME}/.pyenv/bin/get-pip.py ]; then
+  wget -O ${HOME}/.pyenv/bin/get-pip.py https://bootstrap.pypa.io/get-pip.py
+fi
+
+export PYENV_ROOT="${HOME}/.pyenv"
+export PATH="${PYENV_ROOT}/bin:${PATH}"
+
+if command -v pyenv 1>/dev/null 2>&1; then eval "$(pyenv init -)"; fi
+
+${PYENV_ROOT}/plugins/python-build/install.sh
+
+for short_ver in "${py_versions[@]}"; do
+  echo "Checking Python ${short_ver}";
+  if [ -z "${short_ver##*.*}" ]; then
+    export long_ver=$(pyenv install -l | \
+      grep -Po "(?<=\s)[0-9\.]+$" | \
+      grep "${short_ver}." | \
+      tail -n1);
+    echo "Installing /usr/local/bin/python${short_ver} (${long_ver}) via pyenv."
+    if [ "${ID}" == "debian" ]; then
+      CFLAGS=-I/usr/include/openssl LDFLAGS=-L/usr/lib python-build ${long_ver} /usr/local/
+    else
+      CFLAGS=-I/usr/include/openssl LDFLAGS=-L/usr/lib64 python-build ${long_ver} /usr/local/
+    fi
+    echo "Updating pip, setuptools, and virtualenv in /usr/local/bin/python${short_ver}"
+    /usr/local/bin/python${short_ver} ${HOME}/.pyenv/bin/get-pip.py
+    /usr/local/bin/python${short_ver} -m pip install -U pip setuptools virtualenv
+  else
+    if [ -f /usr/bin/python${short_ver} ]; then
+      echo "Updating pip, setuptools, and virtualenv in /usr/bin/python${short_ver}"
+      /usr/bin/python${short_ver} ${HOME}/.pyenv/bin/get-pip.py
+      /usr/bin/python${short_ver} -m pip install -U pip setuptools virtualenv
+    fi
+  fi
+done