Use correct HTTP error codes

app/api/routes/product_routes.py

@@ -40,12 +40,12 @@ def create_product_listing():
 	price = request.json.get('price')
 
 	if name is None or price is None:
-		return abort(401)
+		return abort(400)
 
 	float_price = float(price)
 
 	if not isinstance(float_price, float):
-		return abort(401)
+		return abort(400)
 
 	result, status_code = ProductService.create_listing(user_id, name, float_price)