Ну получается получить данные с OpenWeatherMap

Начал обучатся Python, c написания простых программ. Решил написать программу по погоде , с библиотекой Tkinter. Код работает, но выводится ошибка, из функции search().

Код самой программы. Основан на опыте западного видеоблогера

from tkinter import *
from tkinter import messagebox
from configparser import ConfigParser
import requests


config_file = 'config.ini'
config = ConfigParser()
config.read(config_file)
api_key = config['api_key']['key']

url = 'http://api.openweathermap.org/data/2.5/weather?q={}&appid={}'

def get_weather(city):
    result = requests.get(url.format(city, api_key))
    if result:
        json = result.json()
        # (City, Country, temp_celsius,temp_fahrenheit, icon, weather)
        city = json["name"]
        country = json["sys"]["country"]
        temp_kelvin = json["main"]["temp"]
        temp_celsius = temp_kelvin - 273.15
        temp_fahrenheit = (temp_kelvin - 273.15) * 9/5 + 32
        icon = json["weather"][0]["icon"]
        weather = json["weather"][0]["main"]
        final = (city, country, temp_celsius, temp_fahrenheit, icon, weather)
        return final
    else:
        return None


def search():
    city = city_text.get()
    weather = get_weather(city)
    if weather:
        location_lbl['text'] = '{}, {}'.format(weather[0], weather[1])
        image['bitmap'] = 'weather_icon/{}.png'.format(weather[4])
        temp_lbl['text'] = '{:.2f}C, {:.2f}F'.format(weather[2], weather[3])
        weather_lbl['text'] = weather[5]
    else:
        messagebox.showerror('Error', 'Cannot find city {}'.format(city))

app = Tk()
app.title("Test App")
app.geometry('400x350')

city_text = StringVar()
city_entry = Entry(app, textvariable = city_text)
city_entry.pack()

search_btn = Button(app, text = 'Search Weather', width = 12, command=search)
search_btn.pack()

location_lbl = Label(app, text = 'Location', font = ('bold', 20))
location_lbl.pack()

image = Label(app, bitmap ='')
image.pack()

temp_lbl = Label(app, text = '')
temp_lbl.pack()

weather_lbl = Label(app, text ='')
weather_lbl.pack()


app.mainloop()

Код Config.ini

[api_key]
key = '932d999dbd95894887b3ed90a9d65cc7'