I think the first problem is that pip3 is not installed at all.
When I run:
sudo apt-get -y install python3-pip
Reading package lists… Done
Building dependency tree
Reading state information… Done
python3-pip is already the newest version (8.1.1-2ubuntu0.4).
The following packages were automatically installed and are no longer required:
apt-clone archdetect-deb dmeventd dmraid dpkg-repack gir1.2-timezonemap-1.0
gir1.2-xkl-1.0 grub-common kpartx kpartx-boot libdebian-installer4
libdevmapper-event1.02.1 libdmraid1.0.0.rc16 liblockfile-bin liblockfile1
liblvm2app2.2 liblvm2cmd2.02 libparted-fs-resize0 libreadline5
lockfile-progs lvm2 os-prober pmount python3-icu python3-pam rdate
ubiquity-casper ubiquity-ubuntu-artwork ubuntu-core-launcher
Use ‘sudo apt autoremove’ to remove them.
But pip3 is not on my tx1…