retry many times decorator

[andrea crotti]

On the other hand now that I think again even supposing there is a
permanent error like MySql completely down, retrying continuosly
won't do any harm anyway because the machine will not be able to do
anything else anyway, when someone will fix MySql it would
restart again without human intervention.

So I think I could even just let it retry and use maybe a SMTPHanlder
for the logging errors, to make the notification of problems very
quick..