[Devel] Blacklist and failover

[Alex]

Hello, 

> > disable_dns_blacklist=yes solves trouble, but may be disable it by default, or use of other reply (not 477) makes sense?
> >   
> internally there is a difference between the generic 477 error and the 
> blocking by the blacklists. to be honest, I was to lazy to think about a 
> new error code to reflect this case :(...
> 
> any suggestion on this?

Frankly, I do not know which error code is appropriate, but You could change error description to make source (reason) of error clear.

And also, in my opinion, enabling failure_route in dns blacklisting will be good feature because in this case server does not need to resend requests with delay until timeout, but can trigger failure_route instantly.