Add Errno::EHOSTUNREACH to possible CannotConnectError failures

This happens when the server has disappeared (power failure, kernel
causing a reboot, etc)

Author: reist

lib/redis/client.rb

@@ -307,6 +307,8 @@ def establish_connection
       raise CannotConnectError, "Timed out connecting to Redis on #{location}"
     rescue Errno::ECONNREFUSED
       raise CannotConnectError, "Error connecting to Redis on #{location} (ECONNREFUSED)"
+    rescue Errno::EHOSTUNREACH
+      raise CannotConnectError, "Error connecting to Redis on #{location} (EHOSTUNREACH)"
     end
 
     def ensure_connected