So you checked out code from a place, and whoever runs your subversion server decided to change the URL, or decided to switch from http:// to https:// or to svn+ssh:// … If you’re a noob, you’ll probably just checkout everything again.
Next time this happens just use svn switch
Here’s an example of real life when sourceforge updated the urls of their svn repos, this is what I had to do:
svn switch --relocate https://svn.sourceforge.net/svnroot/frostwire/trunk http://frostwire.svn.sourceforge.net/svnroot/frostwire/trunk
* That command is supposed to be all in one line of course, its written like that for formatting purposes of this blog.