How I can disable log message in stderr?

[tit]

I try send email

$ irb -r gmail
2.3.1 :001 > gmail = Gmail.new 'vezetvsem.test', password
2.3.1 :002 > gmail.deliver do
2.3.1 :003 >   from 'vezetvsem.test@gmail.com'
2.3.1 :004?>  to 'sblohin@yandex.ru'
2.3.1 :005?>  subject 'test'
2.3.1 :006?>  body 'test'
2.3.1 :007?> end

First problem

/Users/tit/.rvm/gems/ruby-2.3.1/gems/ruby-gmail-0.3.1/lib/smtp_tls.rb:39:in `do_tls_start': Object#timeout is deprecated, use Timeout.timeout instead.

Please, fix it, if you can.

Second problem

-> "220 smtp.gmail.com ESMTP 21sm822378ljv.67 - gsmtp\r\n"
<- "EHLO vezetvsem.test\r\n"
-> "250-smtp.gmail.com at your service, [178.76.226.8]\r\n"
-> "250-SIZE 35882577\r\n"
-> "250-8BITMIME\r\n"
-> "250-STARTTLS\r\n"
-> "250-ENHANCEDSTATUSCODES\r\n"
-> "250-PIPELINING\r\n"
-> "250-CHUNKING\r\n"
-> "250 SMTPUTF8\r\n"
<- "STARTTLS\r\n"
-> "220 2.0.0 Ready to start TLS\r\n"
<- "EHLO vezetvsem.test\r\n"
-> "250-smtp.gmail.com at your service, [178.76.226.8]\r\n"
-> "250-SIZE 35882577\r\n"
-> "250-8BITMIME\r\n"
-> "250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH\r\n"
-> "250-ENHANCEDSTATUSCODES\r\n"
-> "250-PIPELINING\r\n"
-> "250-CHUNKING\r\n"
-> "250 SMTPUTF8\r\n"
<- "AUTH PLAIN AHZlemV0dnNlbS50ZXN0QGdtYWlsLmNvbQBzMjE0UzIxNA==\r\n"
-> "235 2.7.0 Accepted\r\n"
<- "MAIL FROM:<vezetvsem.test@gmail.com>\r\n"
-> "250 2.1.0 OK 21sm822378ljv.67 - gsmtp\r\n"
<- "RCPT TO:<sblohin@yandex.ru>\r\n"
-> "250 2.1.5 OK 21sm822378ljv.67 - gsmtp\r\n"
<- "DATA\r\n"
-> "354  Go ahead 21sm822378ljv.67 - gsmtp\r\n"
writing message from String
wrote 288 bytes
-> "250 2.0.0 OK 1500626420 21sm822378ljv.67 - gsmtp\r\n"
<- "QUIT\r\n"
-> "221 2.0.0 closing connection 21sm822378ljv.67 - gsmtp\r\n"

Every time gmail gem write in stderr this log.
If I run my script with this gem in cron, I have recived error mail from cron with this log.
I solved this problem for next code. Before use send email by gmail gem I:

stderr = File.new '/dev/null', 'w'
$stderr.reopen stderr

Please, add optional parameter to gem, ex. debug: false.

Sorry for my bad english...