Reapply "Tail the Sauce Connect log"

This reverts commit 5ad1c8f.

Author: davidsbailey

docker/ci/scripts/ui_tests.sh

@@ -7,13 +7,4 @@
 
 source docker/ci/scripts/prepare_ci_tests.sh
 
-# Set up trap to dump Sauce Connect log on exit (success or failure)
-function dump_sc_log() {
-  if [ -f log/sc.log ]; then
-    echo "Sauce Connect log:"
-    cat log/sc.log
-  fi
-}
-trap dump_sc_log EXIT
-
 bundle exec rake ci:run_ui_tests

lib/rake/ci.rake

@@ -123,6 +123,8 @@ namespace :ci do
     use_saucelabs = !ui_test_browsers.empty?
     if use_saucelabs || test_eyes?
       Cdo::SauceConnect.start_sauce_connect(daemonize: true)
+      # Tail the Sauce Connect log for real-time visibility in CI (from beginning of file)
+      RakeUtils.exec_in_background 'tail -f -n +1 log/sc.log | sed "s/^/[SC] /"'
     end
     RakeUtils.wait_for_url('http://localhost-studio.code.org:3000')
     Dir.chdir('dashboard/test/ui') do