The SVN repositories we're importing have URLs ending with a /.

When trying to access the information about the origin via its URL, the webui fails with a 404 error:

https://archive.softwareheritage.org/api/1/origin/53271965/ > works
https://archive.softwareheritage.org/api/1/origin/svn/url/http://parallel-project.googlecode.com/svn/ > no such origin
https://archive.softwareheritage.org/api/1/origin/svn/url/http://parallel-project.googlecode.com/svn// > plain 404 error