Merge branch 'jc/run-command-report-exec-failure-fix' into maint

A recent update accidentally squelched an error message when the
run_command API failed to run a missing command, which has been
corrected.

* jc/run-command-report-exec-failure-fix:
run-command: report exec failure

diff --cc run-command.c
Simple merge

diff --cc t/t0061-run-command.sh
index cf932c851411e5abd992005de474cc095abecead,8a484878ec8a95f2f72b768056663b971f19f1b5..96bf6d6a7d0145334666fcd15373bad6ac66fd67
--- 1/t/t0061-run-command.sh
--- 2/t/t0061-run-command.sh
+++ b/t/t0061-run-command.sh
@@@ -11,9 -11,11 +11,10 @@@ cat >hello-script <<-EO
        #!$SHELL_PATH
        cat hello-script
  EOF
 ->empty
  
  test_expect_success 'start_command reports ENOENT (slash)' '
-       test-tool run-command start-command-ENOENT ./does-not-exist
+       test-tool run-command start-command-ENOENT ./does-not-exist 2>err &&
+       test_i18ngrep "\./does-not-exist" err
  '
  
  test_expect_success 'start_command reports ENOENT (no slash)' '