Fix build errors

Fix builld errors

app.py

@@ -25,13 +25,15 @@ def fetch_binance_price(symbol: str = "BTCUSDT") -> str:
         symbol (str): Trading pair symbol (e.g. 'BTCUSDT')
     """
 
-    url = f"https://api.binance.com/api/v3/ticker/price?symbol={symbol.upper()}"
+    symbol = symbol.upper() #just in case
+    
+    url = f"https://api.binance.com/api/v3/ticker/price?symbol={symbol}"
     
     try:
         response = requests.get(url)
         response.raise_for_status()  # Raise exception for 4XX/5XX status codes
         data = response.json()
-        return f'The price for {data[symbol]} is {[data[price]}'
+        return f"The price for {data[symbol]} is {data[price]}"
     except requests.RequestException as e:
         print(f"Error fetching data: {e}")
         raise