Problem in autocompletion: elm-stuff not found!

[tanrax]

Everything works perfectly except autocomplete. The next error pops up.

Error detected while processing function elm#Complete[28]..<SNR>114_elmOracle:                                                                                                                                                                      
`elm-stuff` not found! run `elm-package install` for autocomplete.                                                               

Neovim v0.3.1
Ubuntu 18.10

Command previously executed when opening the editor
npm -g install elm elm-test elm-oracle elm-format.