1.5.0rc2 email plugin warning unsupported popen on centos 6.x

[jordansissel]

(This issue was originally filed by @sbarrier at elastic/logstash#2838)

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On Centos 6.x the email plugin work but generate a warning message :

/opt/logstash/vendor/bundle/jruby/1.9/gems/mail-2.6.3/lib/mail/network/delivery_methods/sendmail.rb:72 warning: unsupported popen option: err

the sendmail.rb line 72 is the following IO.popen

def self.popen(command, &block)
 IO.popen command, 'w+', :err => :out, &block
end

Centos use Postfix by default, the sendmail binary is a link :
lrwxrwxrwx. 1 root root 21 Nov 6 2013 /usr/sbin/sendmail -> /etc/alternatives/mta
lrwxrwxrwx. 1 root root 26 Nov 6 2013 /etc/alternatives/mta -> /usr/sbin/sendmail.postfix

[markdesouza]

This problem also exists in Debian 7 (running postfix), Logstash version 1.5.1-1

[jeremy]

Same as mikel/mail#904

JRuby doesn't support the :err option to IO.popen.