Atlassian has changed the way it wants us to send authentication headers.
they want the username:apikey encoded in base64 and that gets stuffed into "authorization: basic" header.
Actually I guess this is normal-ish for basic-auth..
here is their "help" page
https://developer.atlassian.com/cloud/jira/platform/basic-auth-for-rest-apis/

here's how I did it and it seems to work:

auth_parts=(instance['user']+":"+instance['apikey']).encode('ascii')
auth_str=base64.b64encode(auth_parts).decode('ascii')
headers={'Authorization' : 'Basic '+auth_str,'Content-Type':'application/json'}

not being a python programmer I have just hacked this into your util.py in the "get_with_cache" and "do_post" "do_put" functions, so I'm sure you can design a more elegant way to integrate it.

Hello
I have encountered an error. Can you tell me how to fix it?
Looking forward to your reply

Traceback (most recent call last):
File "jira_search_replace.py", line 87, in
main()
File "jira_search_replace.py", line 15, in main
issues=get_issues(config)
File "jira_search_replace.py", line 27, in get_issues
data=util.do_post(config['instance'],'search',post_data)
File "/scripts/jira_search_replace/util.py", line 60, in do_post
return handle_status(url,data,r)
File "/scripts/jira_search_replace/util.py", line 85, in handle_status
log_error(url,r.status_code,r.reason,r.text,json.dumps(data,indent=2))
File "/scripts/jira_search_replace/util.py", line 14, in log_error
f.write(arg+'\n')
TypeError: unsupported operand type(s) for +: 'int' and 'str'