Problem loading custom preconditions Ant/Jenkins

I have a set of custom (written in Java7) pre-conditions and some changesets that use them.  I call the changesets from an Ant (1.8.2) script that I execute in a terminal window (Mac 10.8.x).  Ant script from terminal works fine.

When we do our builds using Jenkins, however (same versions of everything), the pre-conditions cannot be loaded and the changesets that use the pre-conditions fail.

The error is:

“Could not open custom precondition class …”

From the source it looks like a pretty straightforward Class.forName call, though there is a comment the specifically calls out an issue with Ant.

Oh, one more thing:  we have a CustomSqlChange in the same change log, and it loads and executes without error.  It is only the custom pre-conditions that fail.



Oh, and one more one more thing.

I’ve run Ant in debug mode from both the terminal and Jenkins and, while there is a huge volume of information that makes it difficult to know for sure, but the class loading (Ant will tell from where it is loading a particular class) looks to be the same to me.  I can try and nail that down to 100% certainty if it will help.