Azure discontinued support for ubuntu 16.04. Welcome to a new decade.

azure-pipelines.yml

@@ -4,19 +4,13 @@ jobs:
 
 - job: Linux
   pool:
-    vmImage: 'ubuntu-16.04'
-  container:
-    image: 'ubuntu:18.04'
-    options: "--name ci-container -v /usr/bin/docker:/tmp/docker:ro"
+    vmImage: 'ubuntu-20.04'
   steps:
-  - script: |
-      /tmp/docker exec -t -u 0 ci-container \
-      sh -c "apt-get update && DEBIAN_FRONTEND=noninteractive apt-get -o Dpkg::Options::="--force-confold" -y install sudo"
-    displayName: Set up sudo
   - checkout: self
     submodules: true
   - script: |
-      sudo apt-get install -y \
+      sudo apt-get update
+      DEBIAN_FRONTEND=noninteractive sudo apt-get install -y \
         cmake libgmp-dev libmpfr-dev libmpc-dev \
         libboost-all-dev bison texinfo \
         ruby flex curl