bad request error when connecting to Imgur via pyimgur

Question

Here I am trying to create an album in Imgur via pyimgur

import configparser
import webbrowser
import pyimgur
from tkinter import *

client_id = config['credentials']['client_id']
client_secret = config['credentials']['client_secret']
client = pyimgur.Imgur(client_id, client_secret)

if not config['credentials']['pin']:
    def write():
        INPUT = entry.get()
        config.set("credentials", "pin", INPUT)
        with open("config.ini", 'w') as i:
            config.write(i)
        config_set.destroy()

    config_set = Tk()
    config_set.title('Imgur settings')

    Label(config_set, text='Type your PIN:').pack(padx=8, pady=8)

    entry = Entry(config_set, justify='center')
    entry.pack(padx=8, pady=8)

    Button(config_set, text='OK', command=write).pack(padx=8, pady=8)

    auth_url = client.authorization_url('pin')
    webbrowser.open(auth_url)
else:
    pin = config['credentials']['pin']
    client.exchange_pin(pin)

client.create_album("album", "descr")

The main problem is in that part of the code:

else:
        pin = config['credentials']['pin']
        client.exchange_pin(pin)

Cliend_id and client_secret is defined, of course. if not config['credentials']['pin']:** works** as it should. The error is:

Exception in Tkinter callback
Traceback (most recent call last):
  File "D:\Apps\Python\lib\tkinter\__init__.py", line 1921, in __call__
    return self.func(*args)
  File "C:\Users\LEGION\PycharmProjects\pythonProject\Province Helper.py", line 445, in image_imgur
    client.exchange_pin(pin)
  File "C:\Users\LEGION\PycharmProjects\pythonProject\venv\lib\site-packages\pyimgur\__init__.py", line 832, in exchange_pin
    result = self._send_request(EXCHANGE_URL.format(self._base_url),
  File "C:\Users\LEGION\PycharmProjects\pythonProject\venv\lib\site-packages\pyimgur\__init__.py", line 731, in _send_request
    result = request.send_request(url, verify=self.verify, **kwargs)
  File "C:\Users\LEGION\PycharmProjects\pythonProject\venv\lib\site-packages\pyimgur\request.py", line 102, in send_request
    resp.raise_for_status()
  File "C:\Users\LEGION\PycharmProjects\pythonProject\venv\lib\site-packages\requests\models.py", line 1021, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: https://api.imgur.com/oauth2/token

Thanks for the helping!