See email from Github:

What you need to do Our records indicate that you've used `runs-on: macOS-10.14` in the following repositories over the last 7 days: nerdvegas/rez. Please update workflows in those repositories and change the line `runs-on: macOS-10.14` to `runs-on: macOS-latest`.
AcademySoftwareFoundation · Nov 8, 2019 · 59e4738 · 59e4738
1 parent f04ce16
commit 59e4738
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/.github/workflows/mac.yaml b/.github/workflows/mac.yaml
@@ -18,7 +18,7 @@ jobs:
     strategy:
       matrix:
         os-version:
-          - '10.14'
+          - 'latest'
         python-version:
           - '2.7'
           - '3.6'