spritesmith | Utility that takes sprites

Try defining your "sprite" task before it gets called in the "local-development" task (and any others that may fall into the same pattern).

When creating tasks via the gulp.task(...) form you do need to have those tasks created (so they can be registered) prior to their being called. Otherwise you will forward-referencing them.

Forward references

A forward reference is when you compose tasks, using string references, that haven't been registered yet. This was a common practice in older versions, but this feature was removed to achieve faster task runtime and promote the use of named functions.

In newer versions, you'll get an error, with the message "Task never defined", if you try to use forward references.

• from Forward reference documentation

One advantage of the function myGulpTask() {...} form of creating tasks is that do not need to be declared prior to calling them.