It's more than that. We want you to fully understand the patch, and to spot errors in it even before the glib developers find them.
It's unlikely that the glib code would contain errors that Gustavo could spot, before or after cleaning up the patch (no offense to Gustavo meant!). However, a more likely cause of errors would be that the adoption of the code to a new environment breaks an unspoken assumption made by the code. Only truly understanding the code would reveal such assumptions.
We want you to provide a minimalistic patch, that just implements the required functionality, and nothing else. We want the patch to be maintainable due to it being easy to read and follow, instead of being maintainable due to the fact that it is identical with some code elsewhere in the world.
Right. Just say no to "copy-and-paste code reuse". --Guido van Rossum (home page: http://www.python.org/~guido/)