The svn patch command was added in SVN 1.7.0 (1). We now check the

version of svn prior to attempting to execute svn patch and report

to the user that their version of svn does not support the patch

command if it is less than 1.7.0.
(1): https://subversion.apache.org/docs/release-notes/1.7.html#patch

Ran unit tests.
Able to run rbt patch when using SVN 1.7.0 and above. Not able to

run rbt patch when using SVN prior to 1.7.0.