Merge #2929

2929: Maybe fix fetchmail when used with pop3 r=nextgens a=nextgens

## What type of PR?

bug-fix

## What does this PR do?

Fix fetchmail when used with pop3.

### Related issue(s)
- closes #2928 

## Prerequisites
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [ ] In case of feature or enhancement: documentation updated accordingly
- [x] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/workflow.html#changelog) entry file.


Co-authored-by: Florent Daigniere <nextgens@freenetproject.org>

optional/fetchmail/fetchmail.py

@@ -64,7 +64,7 @@ def run(debug):
                 username=escape_rc_string(fetch["username"]),
                 password=escape_rc_string(fetch["password"]),
                 options=options,
-                folders=folders,
+                folders='' if fetch['protocol'] == 'pop3' else folders,
                 lmtp='' if fetch['scan'] else 'lmtp',
             )
             if debug:

towncrier/newsfragments/2928.bugfix

@@ -0,0 +1 @@
+fix fetchmail when used with POP3: disregard "folders"