Currently a module from concurrent-output is inlined into propellor. This
should be converted to a dependency.

Waiting on concurrent-output reaching Debian stable.

> Well, it's in stable now. Not in oldstable yet, and propellor is still
> supporting the current oldstable, I believe.. --[[Joey]]

[[!tag user/joey]]

> This was attempted again in 2018 and had to be reverted
> in [[!commit b6ac64737b59e74d4aa2d889690e8fab3772d2c6]].
> 
> The strange output I was seeing is the first line 
> of "apt-cache policy apache2" (but not subsequent lines)
> and the ssh-keygen command run by `genSSHFP'`

> Propellor also misbehaved in some other ways likely due to not seeing
> the command output it expected. In particular Git.cloned must have
> failed to see an origin url in git config output, because it nuked and
> re-cloned a git repo (losing data).
> 
> So, it seems that readProcess was somehow leaking output to the console
> and also likely not providing it to the caller. 
> 
> The affected system had libghc-concurrent-output-dev 1.10.5-1 installed
> from debian. That is a somewhat old version and perhaps it was buggy?
> However, I have not had any luck reproducing the problem there running
> readProcess in ghci. --[[Joey]]
