I needed to run tests and fix an issue with Subversion 1.8, and on my recently-updated machine running Ubuntu 16.04 (Xenial), Subversion was installed as 1.9.3, which was the only version in the xenial repository.
So, a quick post of what I did, since googling produced no clear answer.
Install the latest from xenial repository (probably no changes, if you have Svn 1.9.3 installed):
% sudo apt-get install libapr1 libaprutil1 libsvn1
Remove libsvn1, because it is 1.9.3:
% sudo apt-get remove libsvn1
Remove (uninstall) Svn 1.9.3
% sudo apt-get remove subversion
Install downloaded packages “manually”
% sudo dpkg -i ./subversion_1.8.13-1ubuntu3_amd64.deb ./libsvn1_1.8.13-1ubuntu3_amd64.deb
Check version (should be 1.8.13):
% svn --version
Check the package:
% dpkg -l | grep subversion
And that’s it.