Update CircleCI to more modern docker image

See https://circleci.com/developer/images/image/cimg/python

.circleci/config.yml

diff --git a/.circleci/config.yml b/.circleci/config.yml
index d5ff7d6..16d7224 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -6,7 +6,8 @@
 executors:
   bionic:
     docker:
-      - image: buildpack-deps:bionic
+      # 3.6 is the current minimum requirement for emscripten
+      - image: cimg/python:3.6
 
 jobs:
   flake8:
@@ -16,8 +17,8 @@
       - run:
           name: install pip
           command: |
-            apt-get update -q
-            apt-get install -q -y python-pip python3-pip
+            sudo apt-get update -q
+            sudo apt-get install -q -y python-pip python3-pip
       - run: python2 -m pip install --upgrade pip
       - run: python3 -m pip install --upgrade pip
       - run: python2 -m pip install flake8==3.7.8
@@ -34,7 +35,9 @@
       - checkout
       - run:
           name: Install debian packages
-          command: apt-get update -q && apt-get install -q -y cmake build-essential openjdk-8-jre-headless ksh zsh
+          command: |
+            sudo apt-get update -q
+            sudo apt-get install -q -y cmake build-essential openjdk-8-jre-headless ksh zsh
       - run: scripts/test.sh
       - run: scripts/test_source_env.sh
       - run:
@@ -132,9 +135,6 @@
     executor: bionic
     steps:
       - checkout
-      - run:
-          name: install docker
-          command: apt-get update -q && apt-get install -q -y docker.io
       - setup_remote_docker:
           version: 19.03.13
       # Build and test the tip-of-tree build of EMSDK
@@ -149,9 +149,6 @@
     executor: bionic
     steps:
       - checkout
-      - run:
-          name: install docker
-          command: apt-get update -q && apt-get install -q -y docker.io
       - setup_remote_docker:
           version: 19.03.13
       - run:
@@ -170,20 +167,21 @@
     executor: bionic
     steps:
       - checkout
-      - run: apt-get install -q -y curl gnupg
+      - run: |
+          sudo apt-get update -q
+          sudo apt-get install -q -y curl gnupg
       - run: curl -fsSL https://bazel.build/bazel-release.pub.gpg | gpg --dearmor > bazel.gpg
-      - run: mv bazel.gpg /etc/apt/trusted.gpg.d/
-      - run: echo "deb [arch=amd64] https://storage.googleapis.com/bazel-apt stable jdk1.8" | tee /etc/apt/sources.list.d/bazel.list
+      - run: sudo mv bazel.gpg /etc/apt/trusted.gpg.d/
+      - run: echo "deb [arch=amd64] https://storage.googleapis.com/bazel-apt stable jdk1.8" | sudo tee /etc/apt/sources.list.d/bazel.list
       - run:
           name: install pip
-          command: |
-            apt-get update -q
-            apt-get install -q -y python3-pip
+          command: sudo apt-get install -q -y python3-pip
       - run: pip3 install absl-py
       - run:
           name: install bazel
           command: |
-            apt-get install -q -y bazel
+            sudo apt-get install -q -y bazel
+            sudo apt-get update -q
       - run: scripts/test_bazel.sh
 
 workflows: