getmail with python 3 adpatations

I use getmail in mailwizard.
Recently Archlinux has dropped getmail, because it does not support Python 3
(and they are slowly trying to do without python 2 as that is not maintained any more).

So I gave it a try to adapt it such that it works for both Python 3 and Python 2.7.

It is on

https://github.com/rpuntaie/getmail

I made it work for Python 3 and Python 2.7
based on tests with mailwizard using just my emails.
Mailwizard itself uses only the POP3 part,
but I also called getmail separately with an IMAP SSL account.
See below the few tests I did.
This is not really abundant testing, but since gmail is used a lot,
it might work for a lot of people also with Python 3.

@Charles Cazabon:

I have read somewhere that you have reduced your efforts to basic maintenance.

Would that include taking over the changes I made?

Could you expose the code to some more tests?

I made a new major version, 6, because of the breaking changes,
by which python versions older than 2.7 will not work any more.
I did not test such older versions.
I dropped some code that is only for older versions of python.
Other than that I kept my changes minimal.

My tests on Archlinux, which has python=python3:

python2 getmail [email protected] --getmaildir=/home/roland/.local/etc/getmail
python getmail [email protected] --getmaildir=/home/roland/.local/etc/getmail

rcfile::

     [retriever]
     type = SimplePOP3SSLRetriever
     server = mail.upcmail.at
     username = [email protected]
     port = 995
     password_command = ("pass", "magenta.at/[email protected]")

     [destination]
     type = Maildir
     path = /home/roland/Mail/[email protected]/INBOX/

     [options]
     read_all = true
     delete = true
     #message_log = /home/roland/.local/var/log/getmail.log

python2 getmail [email protected] --getmaildir=/home/roland/.local/etc/getmail
python getmail [email protected] --getmaildir=/home/roland/.local/etc/getmail

rcfile::

     [retriever]
     type = SimpleIMAPSSLRetriever
     server = imap.gmail.com
     username = [email protected]
     port = 993
     password_command = ("pass", "gmail/[email protected]")

     [destination]
     type = Maildir
     path = /home/roland/Mail/[email protected]/INBOX/

     [options]
     read_all = true
     delete = true
     #message_log = /home/roland/.local/var/log/getmail.log