Use bail out instead of throw (#27)

lib/compare-results/index.js

@@ -3,18 +3,12 @@ const path = require('path');
 const fs = require('fs');
 const _ = require('highland');
 const diag = console.log.bind(console, '# ');
-function throwIncorrectArgumentError() {
-    throw new Error(`master branch and PR artifact file paths required
-    Usage: node lib/compare-results master.tap test262.tap
-    `);
-}
 
 console.log('TAP version 13');
 
-function throwMasterArtifactOutOfSyncError() {
-    throw new Error(`master branch and PR artifacts are out of sync. Was test262 sha updated in babel-test-runner?
-    Consider re-running the master branch test262 job to update the master branch artifact first!
-    `);
+function bailOut(reason) {
+    console.log(`Bail out! ${reason}`);
+    process.exit(0); // tap-mocha-reporter will report correct failure code to CircleCI
 }
 
 function getFileNameFromTitle(title) {
@@ -33,16 +27,15 @@ async function main() {
     const masterArtifactFileArg = process.argv[2];
     const prArtifactFileArg = process.argv[3];
     if (!(masterArtifactFileArg && prArtifactFileArg)) {
-        throwIncorrectArgumentError();
+        bailOut(`master branch and PR artifact file paths required. Usage: node lib/compare-results master.tap test262.tap`);
     }
     const masterArtifactFilePath = path.resolve(process.cwd(), masterArtifactFileArg);
     const prArtifactFilePath = path.resolve(process.cwd(), prArtifactFileArg);
 
     const [masterTests, prTests] = await Promise.all([parseTestResults(masterArtifactFilePath), parseTestResults(prArtifactFilePath)]);
 
     if (masterTests.length !== prTests.length) {
-        console.error('Master and PR artifacts out of sync! Reason: Different number of tests.');
-        throwMasterArtifactOutOfSyncError();
+        bailOut(`master branch and PR artifacts are out of sync. Possible reasons include intermittent-tests.txt or test262 sha was updated. Consider re-running the master branch test262 job to update the master branch artifact first!`);
     }
     const masterTestsMap = masterTests.reduce((acc, test) =>  {
         if (test.type === 'assertion') {