Bug 1841: LTS Support

Updates base to Ubuntu 20.04
Updates python to 3.8
Updates pip dependencies to more recent versions
Adds apt cache to stage 2 dockerfile
Change stage 3 base image to Ubuntu 20.04 so we can use
python3.8

Fixes bug 1841

Change-Id: I442d0ecf09f033946bbbc3301fd8de54382a4195
Signed-off-by: beierlm <mark.beierl@canonical.com>
diff --git a/docker/PLA/Dockerfile b/docker/PLA/Dockerfile
index 8d4350b..36865e5 100644
--- a/docker/PLA/Dockerfile
+++ b/docker/PLA/Dockerfile
@@ -13,16 +13,28 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-FROM ubuntu:18.04 as INSTALL
+FROM ubuntu:20.04 as INSTALL
+
+ARG APT_PROXY
+RUN if [ ! -z $APT_PROXY ] ; then \
+    echo "Acquire::http::Proxy \"$APT_PROXY\";" > /etc/apt/apt.conf.d/proxy.conf ;\
+    echo "Acquire::https::Proxy \"$APT_PROXY\";" >> /etc/apt/apt.conf.d/proxy.conf ;\
+    fi
+
+ARG APT_PROXY
+RUN if [ ! -z $APT_PROXY ] ; then \
+    echo "Acquire::http::Proxy \"$APT_PROXY\";" > /etc/apt/apt.conf.d/proxy.conf ;\
+    echo "Acquire::https::Proxy \"$APT_PROXY\";" >> /etc/apt/apt.conf.d/proxy.conf ;\
+    fi
 
 RUN DEBIAN_FRONTEND=noninteractive apt-get --yes update && \
     DEBIAN_FRONTEND=noninteractive apt-get --yes install \
-    gcc=4:7.4.* \
-    python3=3.6.* \
-    python3-dev=3.6.* \
-    python3-setuptools=39.0.* \
-    curl=7.58.* && \
-    python3 -m easy_install pip==21.0.1 setuptools==51.0.0
+    gcc=4:9.3.* \
+    python3=3.8.* \
+    python3-dev=3.8.* \
+    python3-pip=20.0.2* \
+    python3-setuptools=45.2.* \
+    curl=7.68.*
 
 ARG PYTHON3_OSM_COMMON_URL
 ARG PYTHON3_OSM_PLA_URL
@@ -42,15 +54,24 @@
 RUN tar -zxf /minizinc.tgz && \
     mv /MiniZincIDE-2.4.2-bundle-linux /minizinc
 
-FROM ubuntu:18.04
-LABEL authors="Lars-Göran Magnusson"
+#######################################################################################
+FROM ubuntu:20.04 as FINAL
+
+ARG APT_PROXY
+RUN if [ ! -z $APT_PROXY ] ; then \
+    echo "Acquire::http::Proxy \"$APT_PROXY\";" > /etc/apt/apt.conf.d/proxy.conf ;\
+    echo "Acquire::https::Proxy \"$APT_PROXY\";" >> /etc/apt/apt.conf.d/proxy.conf ;\
+    fi
 
 RUN DEBIAN_FRONTEND=noninteractive apt-get --yes update && \
-    DEBIAN_FRONTEND=noninteractive apt-get --yes install python3-minimal=3.6.* \
+    DEBIAN_FRONTEND=noninteractive apt-get --yes install \
+    python3-minimal=3.8.* \
     && rm -rf /var/lib/apt/lists/*
 
+LABEL authors="Lars-Göran Magnusson"
+
 COPY --from=INSTALL /usr/lib/python3/dist-packages /usr/lib/python3/dist-packages
-COPY --from=INSTALL /usr/local/lib/python3.6/dist-packages  /usr/local/lib/python3.6/dist-packages
+COPY --from=INSTALL /usr/local/lib/python3.8/dist-packages /usr/local/lib/python3.8/dist-packages
 COPY --from=INSTALL /usr/bin/osm* /usr/bin/
 COPY --from=INSTALL /minizinc /minizinc