code: function formatErrors(errors, formatters, errorType) {
    const format = (formatter) => formatter(errors, errorType) || [];
    const flatten = (accum, curr) => accum.concat(curr);
  
    return formatters.map(format).reduce(flatten, [])
  }
docs: Applies formatters to all AnnotatedErrors.
  
  A formatter has the following signature: FormattedError => Array<String>.
  It takes a formatted error produced by a transformer and returns a list
  of log statements to print.