[[!metatitle="testremote of external special remote fails with 'Cannot run git-annex-remote-!dne!'"]]

### Please describe the problem.

When git-annex has not recently used a remote, there appears to be a race condition where sometimes it will fail with "git-annex: Cannot run git-annex-remote-!dne! -- Make sure it's in your PATH and is executable."

### What steps will reproduce the problem?

This test script will trigger it: https://gitlab.com/DanielDent/git-annex-remote-rclone/blob/demo-race-condition/.gitlab-ci.yml
Output: https://gitlab.com/DanielDent/git-annex-remote-rclone/builds/2167279

This test script works: https://gitlab.com/DanielDent/git-annex-remote-rclone/blob/demo-race-condition-2/.gitlab-ci.yml

But the reason it works is because it's using "git-annex testremote GA-rclone-CI --fast || git-annex testremote GA-rclone-CI --fast" - it fails the first time, and then works the second time.
Output: https://gitlab.com/DanielDent/git-annex-remote-rclone/builds/2167316

This test script doesn't trigger it: https://gitlab.com/DanielDent/git-annex-remote-rclone/blob/master/.gitlab-ci.yml
Output: https://gitlab.com/DanielDent/git-annex-remote-rclone/builds/2166902

The 'git-annex copy test --to GA-rclone-CI' line prior to the 'testremote' invocation seems to warm caches and avoids having the bug trigger.

> [[fixed|done]] --[[Joey]]
