[GUIDES] Changed the LANGUAGE variable to GUIDES_LANGUAGE to mini…

…mize conflicts with regular environment variables (eg. in Ubuntu)

railties/guides/rails_guides/generator.rb

@@ -38,9 +38,10 @@
 #     Note that if you are working on a guide generation will by default process
 #     only that one, so ONLY is rarely used nowadays.
 #
-#   LANGUAGE
-#     Use LANGUAGE when you want to generate translated guides in <tt>source/<LANGUAGE></tt>
-#     folder (such as <tt>source/es</tt>). Ignore it when generating English guides.
+#   GUIDES_LANGUAGE
+#     Use GUIDES_LANGUAGE when you want to generate translated guides in
+#     <tt>source/<GUIDES_LANGUAGE></tt> folder (such as <tt>source/es</tt>).
+#     Ignore it when generating English guides.
 #
 #   EDGE
 #     Set to "1" to indicate generated guides should be marked as edge. This
@@ -67,7 +68,7 @@ class Generator
     GUIDES_RE = /\.(?:textile|html\.erb)$/
 
     def initialize(output=nil)
-      @lang = ENV['LANGUAGE']
+      @lang = ENV['GUIDES_LANGUAGE']
       initialize_dirs(output)
       create_output_dir_if_needed
       set_flags_from_environment