Fix syntax errors and update focal image.

.github/workflows/build_docker.yml

@@ -2,8 +2,6 @@
 name: Build & deploy Docker images
 
 on:
-  schedule:
-    - cron: "0 6,18 * * *"
   push:
     paths:
       - "docker/Dockerfile*"
@@ -21,16 +19,16 @@ jobs:
     - uses: actions/checkout@v3
       with:
         submodules: 'recursive'
-    - name: ${{ format('Build {0} image (& Publish - Release Only)', matrix.distro) }}
+    - name: ${{ format('Build & Publish `dev` {0} image', matrix.distro) }}
       uses: docker/build-push-action@v2
       with:
         username: edran
         password: ${{ secrets.DOCKERHUB_TOKEN }}
-        dockerfile: ${{ format('docker/Dockerfile-{0}', matrix.distro) }}
-        tags: dev
+        file: ${{ format('docker/Dockerfile-{0}', matrix.distro) }}
+        tags: ${{ format('fairnle/nle-{0}', matrix.distro) }}:latest
         tag_with_sha: true
         add_git_labels: true
-        push: ${{ github.event_name == "push" }} # Build on PR, Push on Merge.
+        push: ${{ github.event_name == 'push' }} # Build on PR, Push on Merge.
     - name: Check Version Matches Release Tag (Release Only)
       if: github.event_name == 'release' && github.event.action == 'released'
       run: |
@@ -43,9 +41,9 @@ jobs:
       with:
         username: edran
         password: ${{ secrets.DOCKERHUB_TOKEN }}
-        dockerfile: ${{ format('docker/Dockerfile-{0}', matrix.distro) }}
+        file: ${{ format('docker/Dockerfile-{0}', matrix.distro) }}
         tags: |
           ${{ format('fairnle/nle-{0}', matrix.distro) }}:latest, 
-          ${{ format('fairnle/nle-{0}', matrix-distro) }}:${{ github.event.release.tag_name }}
+          ${{ format('fairnle/nle-{0}', matrix.distro) }}:${{ github.event.release.tag_name }}
         add_git_labels: true
         push: true

docker/Dockerfile-bionic

@@ -4,6 +4,7 @@ FROM nvidia/cuda:10.2-cudnn7-devel-ubuntu18.04
 
 ARG PYTHON_VERSION=3.8
 ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1804/x86_64/3bf863cc.pub
 
 RUN apt-get update && apt-get install -yq \
         bison \

docker/Dockerfile-focal

@@ -1,9 +1,11 @@
 # -*- mode: dockerfile -*-
 
-FROM nvidia/cuda:11.0-devel-ubuntu20.04
+FROM nvidia/cuda:11.4.3-devel-ubuntu20.04
 
 ARG PYTHON_VERSION=3.8
 ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64/3bf863cc.pub
+
 
 RUN apt-get update && apt-get install -yq \
         bison \

docker/Dockerfile-xenial

@@ -4,6 +4,8 @@ FROM nvidia/cuda:10.2-cudnn7-devel-ubuntu16.04
 
 ARG PYTHON_VERSION=3.8
 ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu1604/x86_64/3bf863cc.pub
+
 
 RUN apt-get update && apt-get install -yq \
         apt-transport-https \