Use target mode to pull data from a hard disk encrypted with FileVault? I got this message on a MacBook Pro 2012: 


  path /system/installation/packages/osinstall.mpkg appears to be missing or damaged


The first thing to do is to safe data. The hard disk is encrypted with FileVault.

Is it possible to plug it to another MacBook Pro (running High Sierra or El Capitan) and pull the data?
Yes, 

Boot the Mac you want the data from into target disk mode, https://support.apple.com/en-us/HT201462. Connect the two Macs and wait. You should be prompted for the file vault password. After you enter the correct file vault password wait some more. After a few minutes the other mac's drive should mount on the desktop. Now copy over any files you want to keep.