send email on error

[g-normand]

I added a mail management in case of errors if the mailer is configured such as below :

   # ini file settings:
   #[app:main]
   scheduler.mail.host = [host]
   scheduler.mail.username = [from]
   scheduler.mail.password = [pwd]
   scheduler.mail.port = [port]
   scheduler.mail.tls = [True or False]
   scheduler.mail.to = [to]