Add an @ to the severity variable so that the template doesn't break in future versions of Puppet.

templates/object_filelogger.conf.erb

@@ -12,7 +12,7 @@
 
 object FileLogger "<%= @object_name %>" {
   <%- if @severity -%>
-  severity = "<%= severity -%>"
+  severity = "<%= @severity -%>"
   <%- end -%>
   path = "<%= @path -%>"  
 }