[New-bugs-announce] [issue8410] Fix emulated lock to be 'fair'

["Martin v. Löwis"]

> On pthreads plaforms, if the posix_sem functions aren't available
> (when _POSIX_SEMAPHORES isn't defined), the python lock is
> implemented with a mutex and a condition variable.  This appears to
> be the case on Mac OS X, for example. The problem is that this lock
> does not provide fairness to threads trying to acquire it. 

Why do you think condition variables don't provide fairness?