async function modifyJsonpReport ({ reportConfigFilename, approvedFileName }) {
  return fs
    .readFile(reportConfigFilename, 'utf8')
    .then(content => {
      const jsonpReport = modifyJsonpReportHelper(content[0], approvedFileName);
      return fs.writeFile(reportConfigFilename, jsonpReport);
    })
    .catch(err => {
      throw new Error(`Failed to modify the report. ${err.message}.`);
    });
}
Modify the test status of the JSONP report based on the approved file name. JSONP is used
to create the Backstop report in browser. This function ensures the UI consistency after
a user apporves a test in browser and refreshes the report without running a test.

@param {Object} params - the input params
@param {String} params.reportConfigFilename - the path to the html report config file
@param {String} params.approvedFileName - the name of the screenshot that is approved
@return {Promise}