I had the same problem but it got fixed when I removed the cmdtest and yarn and installed yarn using the following commands:
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curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt-get update
sudo apt-get install yarn
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On Ubuntu Linux, you can install Yarn via Debian package repository. You will first need to configure the repository:
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
Then you can simply:
sudo apt-get update && sudo apt-get install yarn
More information [here][1]
[1]: https://yarnpkg.com/lang/en/docs/install/#linux-tab
