ci: upgrade ubuntu 16->20

Author: leepc12

.circleci/config.yml

@@ -7,7 +7,7 @@ defaults: &defaults
 
 machine_defaults: &machine_defaults
   machine: 
-    image: ubuntu-1604:202007-01
+    image: ubuntu-2004:202010-01
   working_directory: ~/chip-seq-pipeline2
 
 make_tag: &make_tag
@@ -22,21 +22,11 @@ commands:
       - run:
           command: |
             sudo apt-get update && sudo apt-get install software-properties-common git wget curl -y
+            sudo apt-get install -y software-properties-common git wget curl python3 python3-pip default-jre
 
-            # install java 11
-            sudo add-apt-repository ppa:openjdk-r/ppa -y
-            sudo apt-get update && sudo apt-get install openjdk-11-jdk -y
-            # automatically set 11 as default java
-            sudo update-java-alternatives -a
-
-            sudo add-apt-repository ppa:deadsnakes/ppa -y
-            sudo apt-get update && sudo apt-get install python3.6 -y
-            sudo wget --no-check-certificate https://bootstrap.pypa.io/get-pip.py
-            sudo python3.6 get-pip.py
-            sudo ln -s /usr/bin/python3.6 /usr/local/bin/python3
-
-            pip3 install --upgrade pip
-            pip3 install caper google-cloud-storage
+            sudo python3 -m pip install --upgrade pip
+            sudo pip3 install PyYAML --ignore-installed
+            sudo pip3 install caper google-cloud-storage
 
   run_workflow_test:
     description: "Run workflow test. This requires an env var INPUT as input JSON's basename."