hop website: yarn build files missing

after installing the neccessary tools I tried to build the website, first for theme, but I got an error when running yarn build in directory antora-ui-hop

:~/workspace/hop/hop-website/antora-ui-hop$ [master]yarn install
00h00m00s 0/0: : ERROR: [Errno 2] No such file or directory: 'install'

Also yarn build and those command in the website root gives the same error. Missing build files?