do not call PyObject_IsSubclass() with an exception set (instead rely on it being cleared when printing it before)

Disable asyncio coroutine tests in Py3.4 as coroutines are not iterables but Task() features this beautiful line of code:
        self._coro = iter(coro)  # Use the iterator just in case.

in generators/coroutines, save away the current exception in the 'return' case of finally clauses as 'return' actually raises an (Async)StopIteration exception

allow yielding exception instances from async generators (previously interpreted them as actual exceptions)

remove accidentally duplicated finaliser code from the coroutine deallocator function as it must get executed earlier than that

add missing preprocessor guard around coroutine dependant code in generic generator utility function

add "--failfast" (stop on first failure) mode to test runner (if supported by Python's unittest module)