I am trying to deploy a simple node.js express-based application to heroku, something which is apparently very basic: https://devcenter.heroku.com/articles/nodejs
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I had a similar problem a few days ago, I think it was because I imported a module created by me and that was what gave the error;
I corrected it like this:
I called the module "path"
const path = require ("path")
and then where my module was imported I made a join of the file path
const myModule = require (path.join (__ dirname, 'MyModule.js'))