fix CI on ubuntu (#549)

* fix CI on ubuntu

* whoops

* run command needs to return true

* better

* typo

* make sure we run in bash

Author: stevengj

.github/workflows/CI.yml

@@ -23,6 +23,9 @@ jobs:
         arch:
           - x64
     steps:
+      - name: Install matplotlib
+        run: if [ "$RUNNER_OS" = "Linux" ]; then sudo apt-get install -y python3-matplotlib; fi
+        shell: bash
       - uses: actions/checkout@v2
       - uses: julia-actions/setup-julia@v1
         with: