(#12012) Remove global override of LANG environment variable

'LANG' environment variable must be set to 'C' in order to reliably parse output of certain commands when building up core Facter facts (to prevent locale differences from affecting the format of the output).  However, it does not need to happen at a global-ish scope whenever facter is 'require'd;  move this behavior from the facter.rb into the local scope of the Facter::Util::Resolution.exec method; restore original value of environment variable after executing any individual command.

Note that, while this behavior is better than the previous behavior (global override), it is still not possible for a custom facter fact to be written to expect any other locale besides 'C'.  Eventually might prefer to find a solution that allows callers to override this behavior if desired.

lib/facter.rb

@@ -39,10 +39,6 @@ module Util; end
   # puts Facter['operatingsystem']
   #
 
-  # Set LANG to force i18n to C
-  #
-  ENV['LANG'] = 'C'
-
   GREEN = ""
   RESET = ""
   @@debug = 0

lib/facter/util/resolution.rb

@@ -64,47 +64,55 @@ def self.with_env(values)
   def self.exec(code, interpreter = nil)
     Facter.warnonce "The interpreter parameter to 'exec' is deprecated and will be removed in a future version." if interpreter
 
-    # Try to guess whether the specified code can be executed by looking at the
-    # first word. If it cannot be found on the PATH defer on resolving the fact
-    # by returning nil.
-    # This only fails on shell built-ins, most of which are masked by stuff in
-    # /bin or of dubious value anyways. In the worst case, "sh -c 'builtin'" can
-    # be used to work around this limitation
-    #
-    # Windows' %x{} throws Errno::ENOENT when the command is not found, so we
-    # can skip the check there. This is good, since builtins cannot be found
-    # elsewhere.
-    if have_which and !Facter::Util::Config.is_windows?
-      path = nil
-      binary = code.split.first
-      if code =~ /^\//
-        path = binary
-      else
-        path = %x{which #{binary} 2>/dev/null}.chomp
-        # we don't have the binary necessary
-        return nil if path == "" or path.match(/Command not found\./)
+
+    ## Set LANG to force i18n to C for the duration of this exec; this ensures that any code that parses the
+    ## output of the command can expect it to be in a consistent / predictable format / locale
+    with_env "LANG" => "C" do
+
+      # Try to guess whether the specified code can be executed by looking at the
+      # first word. If it cannot be found on the PATH defer on resolving the fact
+      # by returning nil.
+      # This only fails on shell built-ins, most of which are masked by stuff in
+      # /bin or of dubious value anyways. In the worst case, "sh -c 'builtin'" can
+      # be used to work around this limitation
+      #
+      # Windows' %x{} throws Errno::ENOENT when the command is not found, so we
+      # can skip the check there. This is good, since builtins cannot be found
+      # elsewhere.
+      if have_which and !Facter::Util::Config.is_windows?
+        path = nil
+        binary = code.split.first
+        if code =~ /^\//
+          path = binary
+        else
+          path = %x{which #{binary} 2>/dev/null}.chomp
+          # we don't have the binary necessary
+          return nil if path == "" or path.match(/Command not found\./)
+        end
+
+        return nil unless FileTest.exists?(path)
       end
 
-      return nil unless FileTest.exists?(path)
-    end
+      out = nil
 
-    out = nil
+      begin
+        out = %x{#{code}}.chomp
+      rescue Errno::ENOENT => detail
+        # command not found on Windows
+        return nil
+      rescue => detail
+        $stderr.puts detail
+        return nil
+      end
 
-    begin
-      out = %x{#{code}}.chomp
-    rescue Errno::ENOENT => detail
-      # command not found on Windows
-      return nil
-    rescue => detail
-      $stderr.puts detail
-      return nil
-    end
+      if out == ""
+        return nil
+      else
+        return out
+      end
 
-    if out == ""
-      return nil
-    else
-      return out
     end
+
   end
 
   # Add a new confine to the resolution mechanism.