Sets @task's result to @error (which @task assumes ownership of)
and completes the task (see g_task_return_pointer() for more
discussion of exactly what this means).
Note that since the task takes ownership of @error, and since the
task may be completed before returning from g_task_return_error(),
you cannot assume that @error is still valid after calling this.
Call g_error_copy() on the error if you need to keep a local copy
as well.
Sets @task's result to @error (which @task assumes ownership of) and completes the task (see g_task_return_pointer() for more discussion of exactly what this means).
Note that since the task takes ownership of @error, and since the task may be completed before returning from g_task_return_error(), you cannot assume that @error is still valid after calling this. Call g_error_copy() on the error if you need to keep a local copy as well.
See also g_task_return_new_error().