Solution for Maven Build Failure Unable to tag SCM error
When doing a mvn release:prepare you might run into the below error. This post provides a solution for the error:

[INFO] ------------------------------------------------------------------------
[INFO] Unable to tag SCM
Provider message:
The svn tag command failed.
Command output:
svn: Path '' does not exist in revision 229

When you run into this issue, you will have to do an svn update and follow it up with a mvn release:prepare command.

This seems to be an issue with the way maven works with svn.  Doing an svn update may not update any files, but yet it will allow the tag to be complete and the build to be successful.