Cannot find module '/home/circleci/repo/env'

I’m trying to build a nodejs project. We use an env.js file which is not part of the repository.
I don’t want/need to use an env.js file on CircleCI as I set up environment variables.

When trying to run the ‘yarn test’ setp my project, I get the following error:

/home/circleci/repo/node_modules/mocha/node_modules/yargs/yargs.js:1163
      else throw err
           ^

Error: Cannot find module '/home/circleci/repo/env'

I assume this is because no env file is present? How do I resolve this as I don’t want to add an env file? Or can I maybe just add an empty one on CircleCI (not in the repository)?

Thanks in advance!