message: Patch dangerfile to only do use strict checks on non-es modules
  ES modules are strict mode by default, so the check should look
  for use of "import"/"export" to determine if flagging is required.
diff: @@ -86,11 +86,15 @@ const noFlowFiles = newJsFiles
  raiseIssueAboutPaths(warn, noFlowFiles, '@flow');
  +// based on assumptions from https://github.com/nodejs/node/wiki/ES6-Module-Detection-in-Node
  +// basically it needs to contain at least one line with import or export at the
  +// beginning of it, followed by a space; any content thereafter doesn't matter
  +const esModuleRegex = /^(import|export)\s/g;
  -// Ensure the use of 'use strict'; on all files
  +// Ensure the use of 'use strict' on all non-ES module files
  const noStrictFiles = newJsFiles.filter(filepath => {
  const content = fs.readFileSync(filepath).toString();
  - return !includes(content, 'use strict');
  + return !esModuleRegex.test(content) && !includes(content, 'use strict');
  });
  raiseIssueAboutPaths(fail, noStrictFiles, "'use strict'");
  