[dev] Check ruby version

Otherwise we get inexplicable errors with pathname or hash.select ...

dev/puppet/bind.rb

 #!/usr/bin/ruby
 
+if RUBY_VERSION < "2.1"
+  puts "This script requires ruby >= 2.1"
+  exit
+end
+
 # See also: https://www.grid5000.fr/mediawiki/index.php/DNS_server
 
 require 'pp'

dev/puppet/conmang5k.rb

 #!/usr/bin/ruby
 
+if RUBY_VERSION < "2.1"
+  puts "This script requires ruby >= 2.1"
+  exit
+end
+
 # This script generates conmang5k/files/<site_uid>/conman.conf from input/, conf/console.yaml and conf/console-password.yaml
 
 require 'pp'

dev/puppet/dhcp.rb

 #!/usr/bin/ruby
 
+if RUBY_VERSION < "2.1"
+  puts "This script requires ruby >= 2.1"
+  exit
+end
+
 require 'pp'
 require 'erb'
 require 'pathname'

dev/puppet/kadeployg5k.rb

 #!/usr/bin/ruby
 
+if RUBY_VERSION < "2.1"
+  puts "This script requires ruby >= 2.1"
+  exit
+end
+
 # This script generates:
 # - kadeployg5k/files/<site_uid>/server_conf[_dev]/clusters.conf from input/
 # - kadeployg5k/files/<site_uid>/server_conf[_dev]/<cluster_uid>-cluster.conf from conf/kadeployg5k.yaml and template/kadeployg5k.yaml.Erb

dev/puppet/lanpowerg5k.rb

 #!/usr/bin/ruby
 
+if RUBY_VERSION < "2.1"
+  puts "This script requires ruby >= 2.1"
+  exit
+end
+
 # This script generates lanpowerg5k/files/<site_uid>/lanpower.conf from conf/console.yaml and conf/console-password.conf
 
 require 'pp'