Dropped lines are never executed by supported Python versions.
The code exists for sake of keeping the same code base for stdlib asyncio and third-party library with the same name.
Since Python 3.4 asyncio is a part of stdlib, asyncio on PyPI is not supported/updated for 2.5 years.
Removing is safe.

The change keeps backward compatibility with old libraries written for `yield from` syntax, both awaiting old-styled coroutines and yielding from new styles async functions are supported.

async def f():
    ...
yield from f()

@asyncio.coroutine
def g():
    ...
await g()

Thus no regressions/deprecations, just removing non-public never executed implementation details.