What does this error say? [CS50 WEB FINANCE]

I am doing CS50 Web track finance buy and this is my code which gives the error given below The error which it is giving is confusing and I dont understand what it is saying as well as how to correct my code. Any help wpuld be appreciated.

def buy():
    """Buy shares of stock"""
    if request.method == "POST":
        symbol = request.form.get("Symbol")
        quote = lookup(symbol)
        # Checking if Quote is available
        if not quote:
            return apology("Quote not Found",403)
        else:
            shares = request.form.get("Shares")
            # Get current user cash
            rows = db.execute("SELECT * FROM users WHERE id=?", session["user_id"])
            cash = rows[0]["cash"]
            print(cash)
            amount = float(shares)*quote["price"]
            if cash < amount:
                return apology("NOT ENOUGH CASH",403)
            else:
                cash -= amount
                # Add to transactions
                db.execute("INSERT INTO transactions (user_id,symbol,price,shares,amount) VALUES(:user_id,:symbol,:price,:shares,:amount)",user_id=session["user_id"],symbol=quote["symbol"],price=quote["price"],shares=shares,amount=amount)
                # update cash in users
                db.execute("UPDATE users SET cash = :cash WHERE id=:user_id",user_id =session["user_id"],cash=cash)
                return redirect("/")
    else:
        return render_template("buy.html")

Error

Traceback (most recent call last):
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/usr/local/lib/python3.7/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python3.7/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/ubuntu/finance/helpers.py", line 34, in decorated_function
    return f(*args, **kwargs)
  File "/home/ubuntu/finance/application.py", line 57, in buy
    quote = lookup(symbol)
  File "/home/ubuntu/finance/helpers.py", line 44, in lookup
    response = requests.get(f"https://cloud-sse.iexapis.com/stable/stock/{urllib.parse.quote_plus(symbol)}/quote?token={api_key}")
  File "/usr/local/lib/python3.7/urllib/parse.py", line 850, in quote_plus
    string = quote(string, safe + space, encoding, errors)
  File "/usr/local/lib/python3.7/urllib/parse.py", line 834, in quote
    return quote_from_bytes(string, safe)
  File "/usr/local/lib/python3.7/urllib/parse.py", line 859, in quote_from_bytes
    raise TypeError("quote_from_bytes() expected bytes")
TypeError: quote_from_bytes() expected bytes
INFO: 192.168.239.121 - - [29/Dec/2020 13:18:22] "POST /buy HTTP/1.0" 500 -
INFO: 192.168.239.121 - - [29/Dec/2020 13:18:23] "GET /static/styles.css HTTP/1.0" 200 -
INFO: 192.168.239.121 - - [29/Dec/2020 13:18:23] "GET /static/favicon.ico HTTP/1.0" 200 -