Protected transfer problem FTP_TLS in Python

Question

I would like to check if a file exists in my FTP server. I have this function:

from ftplib import FTP_TLS
from configparser import ConfigParser

def check_ftp_file_exists(filename):

    config = ConfigParser()
    config.read("config.ini")
    user = config["ftp"]["user"]
    passwd = config["ftp"]["password"]
    ftp = config["ftp"]["host"]

    with FTP_TLS(ftp, user, passwd) as ftp:
        file_list = ftp.nlst()
        if filename in file_list:
            return True
        else:
            return False

This function returns an error:

ftplib.error_perm: 522 Data connections must be encrypted.. Here (How to upload a file on FTPS server using m2crypto) I found that I should use ftp.prot_p(). But this function:

from ftplib import FTP_TLS
from configparser import ConfigParser

def check_ftp_file_exists(filename):

    config = ConfigParser()
    config.read("config.ini")
    user = config["ftp"]["user"]
    passwd = config["ftp"]["password"]
    ftp = config["ftp"]["host"]

    with FTP_TLS(ftp, user, passwd) as ftp:
        ftp.prot_p()
        file_list = ftp.nlst()
        if filename in file_list:
            return True
        else:
            return False

returns another error ftplib.error_perm: 522 SSL connection failed: session reuse required. How can I fix it please?