$ volt get -u tyru/forget-me-not.vim
[INFO] Full building /Users/tyru/.vim/pack/volt/opt directory ...
[INFO] Installing vimrc and gvimrc ...
! github.com/tyru/forget-me-not.vim > upgrade failed
* failed to upgrade plugin: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain
[ERROR] failed to install some plugins
Workarounds
git config --global "url.git@github.com:<user>/.insteadOf" "https://github.com/<user>/"<user>with accessing repo's userThanks
reported by @tennashi