Handle browser launch error events

Without this, in some cases (e.g. no permissions to run Chrome) the
event is unhandled, and the server crashes. It's better to clearly
catch and report this.

Author: pimterry

src/browsers.ts

@@ -83,5 +83,16 @@ export { LaunchOptions };
 
 export const launchBrowser = async (url: string, options: LaunchOptions, configPath: string) => {
     const launcher = await getLauncher(configPath);
-    return await promisify(launcher)(url, options);
+    const browserInstance = await promisify(launcher)(url, options);
+
+    browserInstance.process.on('error', (e) => {
+        // If nothing else is listening for this error, this acts as default
+        // fallback error handling: log & report & don't crash.
+        if (browserInstance.process.listenerCount('error') === 1) {
+            console.log('Browser launch error');
+            reportError(e);
+        }
+    });
+
+    return browserInstance;
 };