[INFO] cloning repository https://github.com/walkgit/serial-assistant
[INFO] running `Command { std: "git" "-c" "credential.helper=" "-c" "credential.helper=/workspace/cargo-home/bin/git-credential-null" "clone" "--bare" "https://github.com/walkgit/serial-assistant" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fwalkgit%2Fserial-assistant", kill_on_drop: false }`
[INFO] [stderr] Cloning into bare repository '/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fwalkgit%2Fserial-assistant'...
[INFO] running `Command { std: "git" "rev-parse" "HEAD", kill_on_drop: false }`
[INFO] [stdout] 3a3bb87d00ce876a74efe5671c7fc2b5d9558ca9
[INFO] checking walkgit/serial-assistant against master#667247db71ea18c4130dd018d060e7f09d589490 for pr-140824
[INFO] running `Command { std: "git" "clone" "/workspace/cache/git-repos/https%3A%2F%2Fgithub.com%2Fwalkgit%2Fserial-assistant" "/workspace/builds/worker-0-tc1/source", kill_on_drop: false }`
[INFO] [stderr] Cloning into '/workspace/builds/worker-0-tc1/source'...
[INFO] [stderr] error: failed to write new configuration file /workspace/builds/worker-0-tc1/source/.git/config.lock
[INFO] [stderr] fatal: could not set 'core.repositoryformatversion' to '0'


failed to checkout https://github.com/walkgit/serial-assistant

Caused by:
    command failed: exit status: 128