Added error handler to web server.

src/web/error.js

@@ -0,0 +1,17 @@
+'use strict';
+
+const logger = require('../logger')(__filename);
+
+function errorHandler(error, req, res, _next) {
+	logger.warn(`Failed to fulfill request to ${req.path}: ${error.message}`);
+
+	if (error.httpCode) {
+		res.status(error.httpCode).send(error.message);
+
+		return;
+	}
+
+	res.status(500).send('Oops... our server messed up. We will be investigating this incident, our apologies for the inconvenience.');
+}
+
+module.exports = errorHandler;