For bpo-32604 I added some subinterpreter-related tests (see #6914) that are causing crashes on a few buildbots. I'm working on fixing the crashes (see #7251). This change temporarily disables the triggering test.
The CPython runtime assumes that there is a one-to-one relationship (for a given interpreter) between PyThreadState and OS threads. Sending and receiving on a channel in the same interpreter was causing crashes because of this (specifically due to a check in PyThreadState_Swap()). The solution is to not switch threads if the interpreter is the same.