Update packages for ubuntu image

Author: melissawm

Diff for: .circleci/config.yml

@@ -13,7 +13,7 @@ jobs:
 
       - run:
           name: Install deps for building atari-py
-          command: sudo apt-get install -y cmake ffmpeg
+          command: sudo apt-get update && sudo apt-get install -y cmake ffmpeg
 
       - run:
           name: Install Python dependencies