Why ?
Well, Capistrano 3 has dropped the support for SVN as source control mechanism. Unable to to implement this in a generic way was the reason quoted. Discussion can be followed on the github issue here - https://github.com/capistrano/capistrano/issues/752
Looks like there are no plans to commit this fix to the branch any time soon and SVN is no more a priority for capistrano. So, i have put together my fix (not very pretty though..) to support SVN and like to share it in case it helps.
Solution -
Install capistrano gem from the source here -
https://github.com/udayakiran/capistrano/tree/3.4.0-svn-scm
This fix is currently made on 3.4.0 on a fresh branch and i am not planning to merge this with trunk any time just to keep this fix a separate one. Just go through the commit history to see the changes made. These changes can be easily applied to later versions of capistrano.
Installation instructions -
Same as installing a gem form any git branch.
A) Add the below line to your Gemfile if you are using one.
gem 'rails', :git => "git://github.com/udayakiran/capistrano.git", :branch => "3.4.0-svn-scm"OR
B) Follow the steps in this stackoverflow answer to build the gem.