added check if bidder == seller and error message

src/tjts5901/views.py

@@ -180,6 +180,10 @@ def bid(id):
     if item.closes_at < datetime.utcnow():
         flash("This item is no longer on sale.")
         return redirect(url_for('views.list_bid'))
+    
+    if item.seller == current_user:
+        flash("You cannot bid on your own item. Bid was not saved.")
+        return redirect(url_for('views.list_bid'))
 
     try:
         # Notice: if you have integrated the flask-login extension, use current_user