function isMochaInternal (line) {
    return (~line.indexOf('node_modules' + slash + 'mocha' + slash)) ||
      (~line.indexOf('node_modules' + slash + 'mocha.js')) ||
      (~line.indexOf('bower_components' + slash + 'mocha.js')) ||
      (~line.indexOf(slash + 'mocha.js'));
  }
@summary
This Filter based on `mocha-clean` module.(see: `github.com/rstacruz/mocha-clean`)
@description
When invoking this function you get a filter function that get the Error.stack as an input,
and return a prettify output.
(i.e: strip Mocha and internal node functions from stack trace).
@returns {Function}