debug2: Control master terminated unexpectedly

[vs49688]

In some situations Travis builds fail with this error. I have no idea what causes it, but it seems extremely inconsistent. This has only ever been seen on Travis builds, never on a local build.

https://travis-ci.org/github/UQ-RCC/nimrodg/jobs/712805294

    [Test worker] TRACE au.edu.uq.rcc.nimrodg.shell.OpenSSHClient - Executing command: /usr/bin/ssh -l user -i /tmp/junit9299936063122352927/openssh-1882757806-key -p 2292 -oPasswordAuthentication=no -oKbdInteractiveAuthentication=no -oChallengeResponseAuthentication=no -oBatchMode=yes -oControlMaster=auto -oControlPersist=yes -oControlPath=/tmp/junit9299936063122352927/openssh-1882757806-control -oStrictHostKeyChecking=no -oUserKnownHostsFile=/dev/null -oLogLevel=DEBUG3 127.0.0.1 -E /tmp/junit9299936063122352927/openssh-1882757806-log01.txt -- scp -q -p -t /asdf
    [Test worker] TRACE au.edu.uq.rcc.nimrodg.shell.OpenSSHClient - Attempting to dump OpenSSH log file at /tmp/junit9299936063122352927/openssh-1882757806-log01.txt
    [Test worker] TRACE au.edu.uq.rcc.nimrodg.shell.OpenSSHClient - debug1: Reading configuration data /home/travis/.ssh/config
    debug1: /home/travis/.ssh/config line 1: Applying options for *
    debug1: /home/travis/.ssh/config line 2: Deprecated option "useroaming"
    debug1: Reading configuration data /etc/ssh/ssh_config
    debug1: /etc/ssh/ssh_config line 19: Applying options for *
    debug1: auto-mux: Trying existing master
    debug2: fd 4 setting O_NONBLOCK
    debug2: mux_client_hello_exchange: master version 4
    debug3: mux_client_forwards: request forwardings: 0 local, 0 remote
    debug3: mux_client_request_session: entering
    debug3: mux_client_request_alive: entering
    debug3: mux_client_request_alive: done pid = 7067
    debug3: mux_client_request_session: session request sent
    debug1: mux_client_request_session: master session id: 2
    debug3: mux_client_read_packet: read header failed: Broken pipe
    debug2: Control master terminated unexpectedly

[vs49688]

Attaching full log for posterity.

log.txt

[vs49688]

Happens when rebased on master: https://travis-ci.org/github/UQ-RCC/nimrodg/builds/712810084

log.txt

[vs49688]

Still happening when 8cb1eb4 is reverted.
https://travis-ci.org/github/UQ-RCC/nimrodg/jobs/712810885

log.txt

[vs49688]

Happening again on GitHub Actions. Logs attached.
logs_6.zip