Migration sources files problem I am trying to migrate a drupal 6 to 8 through drupal migrate ui and i am getting a error with the sources files, drupal 8 is not able to read sites folders due is writting a double slash. 

Does anyone why this happens? 


  Source ID 3125: Cannot read from non-readable stream (http://dev.example.com/example//sites/default/files/)


The URL has an empty part in the path. I tried with full permissions in this folders, source in subdomain, domain, folder, etc.
How are you providing the location of the files?  IIRC, you can give it an absolute path ( /home/www/drupal ) or a URL ( http://www.example.com ).

In either case are you including a final '/'?  If so, try removing it.