Use Socket.gethostname instead of node['fqdn'] which might be nil

debian/patches/0004-Use-Socket.gethostname-for-hostname-information.patch

+From: Christopher Huhn <C.Huhn@gsi.de>
+Date: Fri, 13 Mar 2020 16:15:19 +0100
+Subject: Use Socket.gethostname for hostname information
+
+---
+ lib/chef/handler/mail.rb | 15 +++++++++++----
+ 1 file changed, 11 insertions(+), 4 deletions(-)
+
+diff --git a/lib/chef/handler/mail.rb b/lib/chef/handler/mail.rb
+index c00aaba..3be01cc 100644
+--- a/lib/chef/handler/mail.rb
++++ b/lib/chef/handler/mail.rb
+@@ -16,12 +16,14 @@ require 'chef'
+ require 'chef/handler'
+ require 'erubis'
+ require 'mail'
++require 'socket'
+ 
+ class MailHandler < Chef::Handler
+   attr_reader :options
+   def initialize(opts = {})
+     @options = {
+       :to_address => "root",
++      :from_address => "chef-client@#{Socket.gethostname}",
+       :template_path => File.join(File.dirname(__FILE__), "mail.erb")
+     }
+     @options.merge! opts
+@@ -29,13 +31,18 @@ class MailHandler < Chef::Handler
+ 
+   def report
+     status = success? ? "Successful" : "Failed"
+-    subjectstr = "[CHEF] #{status} chef-client run on #{node.fqdn} (#{node.ipaddress})"
++    subjectstr = format(
++      '[CHEF] %s chef-client run on %s' ,
++      status,
++      Socket.gethostname
++    )
+ 
+     Chef::Log.debug("mail handler template path: #{options[:template_path]}")
+     if File.exists? options[:template_path]
+       template = IO.read(options[:template_path]).chomp
+     else
+-      Chef::Log.error("mail handler template not found: #{options[:template_path]}")
++      Chef::Log.error("mail handler template not found: " +
++                      options[:template_path])
+       raise Errno::ENOENT
+     end
+ 
+@@ -48,10 +55,10 @@ class MailHandler < Chef::Handler
+     bodystr = Erubis::Eruby.new(template).evaluate(context)
+ 
+     to_address = options[:to_address]
+-    from_address = "chef-client@#{node.fqdn}"
++    from_address = "chef-client@#{Socket.gethostname}"
+ 
+     mail = Mail.new do
+-      from     from_address
++      from     options[:from_address]
+       to       to_address
+       subject  subjectstr
+       body     bodystr

debian/patches/series

 0001-get-rid-of-pony-dependency.patch
 0002-add-more-information-and-refactor-format.patch
 0001-No-require-rubygems.patch
+0004-Use-Socket.gethostname-for-hostname-information.patch