--- a/browser/tools/mozscreenshots/mozscreenshots/extension/TestRunner.jsm
+++ b/browser/tools/mozscreenshots/mozscreenshots/extension/TestRunner.jsm
@@ -54,32 +54,32 @@ this.TestRunner = {
                    (new Date()).toISOString().replace(/:/g, "-") + "_" + Services.appinfo.OS];
     let screenshotPath = FileUtils.getFile("TmpD", subDirs).path;
 
     const MOZ_UPLOAD_DIR = env.get("MOZ_UPLOAD_DIR");
     if (MOZ_UPLOAD_DIR) {
       screenshotPath = MOZ_UPLOAD_DIR;
     }
 
-    this.mochitestScope.info("Saving screenshots to:", screenshotPath);
+    this.mochitestScope.info(`Saving screenshots to: ${screenshotPath}`);
 
     let screenshotPrefix = Services.appinfo.appBuildID;
     if (jobName) {
       screenshotPrefix += "-" + jobName;
     }
     screenshotPrefix += "_";
     Screenshot.init(screenshotPath, this._extensionPath, screenshotPrefix);
     this._libDir = this._extensionPath.QueryInterface(Ci.nsIFileURL).file.clone();
     this._libDir.append("chrome");
     this._libDir.append("mozscreenshots");
     this._libDir.append("lib");
 
     let sets = this.loadSets(setNames);
 
-    this.mochitestScope.info(sets.length + " sets:", setNames);
+    this.mochitestScope.info(`${sets.length} sets: ${setNames}`);
     this.combos = new LazyProduct(sets);
     this.mochitestScope.info(this.combos.length + " combinations");
 
     this.currentComboIndex = this.completedCombos = 0;
     this._lastCombo = null;
 
     // Setup some prefs
     Services.prefs.setCharPref("browser.aboutHomeSnippets.updateUrl",