Adrián Bíro

Disable IPv6, to fix slow pip install.

List current values.

$ sysctl net.ipv6.conf.all.disable_ipv6
net.ipv6.conf.all.disable_ipv6 = 0
$ sysctl net.ipv6.conf.default.disable_ipv6
net.ipv6.conf.default.disable_ipv6 = 0

Or on the wifi net.ipv6.conf.wlp0s20f3.disable_ipv6 interface. List all interfaces with netstat -i

$ sysctl net.ipv6.conf.eth0.disable_ipv6 
net.ipv6.conf.eth0.disable_ipv6 = 0

Set 1 to disable.

$ sysctl net.ipv6.conf.all.disable_ipv6=1
$ sysctl net.ipv6.conf.default.disable_ipv6=1
$ sysctl net.ipv6.conf.eth0.disable_ipv6=1

To make it persistent append variable GRUB_CMDLINE_LINUX in /etc/default/grub

Grub2 setup Ubuntu docs

GRUB Arch Wiki

GRUB_CMDLINE_LINUX="ipv6.disable=1"

Update grub settings with grub2-mkconfig -o /boot/grub2/grub.cfg