`thread caused non-unwinding panic. aborting.`

[MichaReiser]

The unwrap call here can fail when the lock got poisoned because of a panic, causing a panic while unwinding

https://github.com/davidbarsky/tracing-tree/blob/12ac87f080223e4147062b62dd0a170f516ad3c3/src/lib.rs#L574

The application doesn't abort when using a different tracing subscriber.

I think a fix here could be to not print to buf but otherwise run the logic "as normal"