yarn install fails with "No such file or directory: 'install'"

[DewiMorgan]

Session log:

# git clone https://github.com/cmengler/fitbit-app-versa4.git
  Cloning into 'fitbit-app-versa4'...
  remote: Enumerating objects: 45, done.
  remote: Counting objects: 100% (45/45), done.
  remote: Compressing objects: 100% (32/32), done.
  remote: Total 45 (delta 11), reused 36 (delta 7), pack-reused 0
  Unpacking objects: 100% (45/45), done.

# cd fitbit-app-versa4/app/
# yarn install
  Command 'yarn' not found, but can be installed with:
  apt install cmdtest

# apt install cmdtest
  Reading package lists... Done
  Building dependency tree
  Reading state information... Done
  The following additional packages will be installed:
    python python-chardet python-cliapp python-markdown python-pkg-resources
    python-pygments python-ttystatus python-yaml
  Suggested packages:
    python-doc python-tk python-xdg python-markdown-doc python-setuptools ttf-bitstream-vera
  The following NEW packages will be installed:
    cmdtest python python-chardet python-cliapp python-markdown python-pkg-resources
    python-pygments python-ttystatus python-yaml
[... installing yarn happened here ...]

# yarn install
  00h00m00s 0/0: : ERROR: [Errno 2] No such file or directory: 'install'
  
# pwd
  /mnt/e/devel/FitBit/fitbit-app-versa4/app
  
# ls
  index.js

Looks like yarn is looking for a file or folder app/install which is not included in this repo?

[wiledal]

Ah you're actually just suppose to run yarn. install is redundant in the installation process! Also, install yarn using npm instead!
https://classic.yarnpkg.com/lang/en/docs/install/#mac-stable
npm install --global yarn.