Deleting a folder from svn repository

Looks like a commit message is required, and you do not have your system configured to launch an editor for you to add one (without specifying on the command line).

Try this:

svn delete http://www.yourrepository.com/svn/folder --message "Deleting"

To avoid similar messages in the future, add something like export SVN_EDITOR="/usr/bin/vim" to your .bash_profile (or something similar for your Mac :))