Fix Hyper's error and make it more useful

src/client/websocket/WebSocketManager.js

@@ -265,7 +265,8 @@ class WebSocketManager extends EventEmitter {
         if (this.client.options.fetchAllMembers) {
           const promises = this.client.guilds.array().map(g => g.fetchMembers());
           Promise.all(promises).then(() => this._emitReady()).catch(e => {
-            this.client.emit(Constants.Event.WARN, `Error on pre-ready guild member fetching - ${e}`);
+            this.client.emit(Constants.Events.WARN, 'Error in pre-ready guild member fetching');
+            this.client.emit(Constants.Events.ERROR, e);
             this._emitReady();
           });
           return;

src/util/Constants.js

@@ -190,6 +190,7 @@ exports.Events = {
   TYPING_STOP: 'typingStop',
   DISCONNECT: 'disconnect',
   RECONNECTING: 'reconnecting',
+  ERROR: 'error',
   WARN: 'warn',
   DEBUG: 'debug',
 };