[Python-checkins] Pin test runner to Ubuntu 18 to un-break CI (GH-24715) (GH-24716)

[ned-deily]

https://github.com/python/cpython/commit/a99860e4022c386df6e51fcc7741b0aeba25d687
commit: a99860e4022c386df6e51fcc7741b0aeba25d687
branch: 3.7
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: ned-deily <nad at python.org>
date: 2021-03-03T12:24:05-05:00
summary:

Pin test runner to Ubuntu 18 to un-break CI (GH-24715) (GH-24716)

(cherry picked from commit 94894dd45e4bad6efb27eac4497b24cdc18b3e2d)

Co-authored-by: Brandt Bucher <brandt at python.org>

Co-authored-by: Brandt Bucher <brandt at python.org>

files:
M .github/workflows/build.yml

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index b3d4b7bab9cdd..e60d315de48c8 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -73,7 +73,7 @@ jobs:
 
   build_ubuntu:
     name: 'Ubuntu'
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-18.04
     needs: check_source
     if: needs.check_source.outputs.run_tests == 'true'
     env: