How to get tracebacks for coroutines?

[HyperHacker <hyperhacker@...>]

I've run into a bit of a hangup in developing an application that
makes heavy use of coroutines. When a coroutine crashes, I can see
where the error occurred, but not a stack traceback.
coroutine.resume() only returns the error message, and I can't wrap
the body in xpcall() because (in 5.1 at least) that's a C function, so
the coroutine becomes unable to yield. So, is there any way to get the
traceback?

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