Log purging goes to stdout breaking scripts

[findepi]

Following #513 (comment), i use mvnd in a script like this

project_version=$(mvnd -B help:evaluate -Dexpression=pom.version -q -DforceStdout --raw-streams)

This breaks, however, if mvnd decides to purge logs.
The variable ends up containing a value like:

372-SNAPSHOT
Purged 18 log files (log available in /Users/findepi/.m2/mvnd/registry/0.7.1/purge-2022-02-25.log)

[gnodet]

@findepi #617 prints the message to the error stream so that you could redirect it to /dev/null without having to disable purge. Would that work for you ?

[findepi]

@gnodet the stderr would do, thanks!
(in my case, i don't even need to redirect it to /dev/null, it simply won't become of shell's variable value)