Ensure UserError is raised with a reason value

This commit addresses the issue fixed in
416cf28; however that commit
discarded the reason attached to the exception.  This should be kept,
since Train::UserError covers a lot of ground and the reason
code can help clients differentiate cause without resorting to
their own parsing of error string.

Signed-off-by: Marc A. Paradise <marc.paradise@gmail.com>

lib/train/extras/command_wrapper.rb

@@ -169,8 +169,8 @@ def self.load(transport, options)
         res = LinuxCommand.new(transport, options)
         verification_res = res.verify
         if verification_res
-          msg, _reason = verification_res
-          raise Train::UserError, "Sudo failed: #{msg}"
+          msg, reason = verification_res
+          raise Train::UserError.new("Sudo failed: #{msg}", reason)
         end
         res
       elsif transport.platform.windows?