re: Running the Code, you need etc/mailman.cfg like so:

USE_LMTP = Yes
add_qrunner('HTTP')

You may optionally set HTTP_HOST = if you want to access the web interface from an external host. 

Also, you may want to test  MTA = 'Postfix' feature.  You should set your /etc/postfix/main.cf like so:

alias_maps = hash:/etc/aliases
    hash:/usr/local/mailman/data/aliases
alias_database = hash:/etc/aliases
virtual_alias_maps = hash:/etc/postfix/virtual
    hash:/usr/local/mailman/data/virtual-mailman
transport_maps = hash:/usr/local/mailman/data/transport
    hash:/etc/postfix/transport
local_recipient_maps = proxy:unix:passwd.byname $alias_maps
    $virtual_alias_maps $transport_maps