fetchcommandwrapper combines download tool aria2 with variable GENTOO_MIRRORS to speed up distfile downloads of Portage by downloading from multiple mirrors at the same time. fetchcommandwrapper integrates with Portage through variables FETCHCOMMAND (and RESUMECOMMAND), hence the name.

# sudo emerge -av app-portage/fetchcommandwrapper

You can then append line source /usr/share/fetchcommandwrapper/make.conf to file /etc/portage/make.conf to ease integration with Portage.

# pip install --user --editable .