Don’t include an extensions list in Roo::Base#file_type_check, and on…

…ly create the warning message if it is to be displayed.

lib/roo/base.rb

@@ -508,24 +508,18 @@ def file_type_check(filename, ext, name, warning_level, packed=nil)
       # getestet, falls es eine gepackte Datei ist.
       filename = File.basename(filename,File.extname(filename))
     end
-    case ext
-    when '.ods', '.xls', '.xlsx', '.csv', '.xml'
-      correct_class = "use #{Roo::CLASS_FOR_EXTENSION[ext]}.new to handle #{ext} spreadsheet files. This has #{File.extname(filename).downcase}"
-    else
-      raise "unknown file type: #{ext}"
-    end
 
     if uri?(filename) && qs_begin = filename.rindex('?')
       filename = filename[0..qs_begin-1]
     end
     if File.extname(filename).downcase != ext
       case warning_level
       when :error
-        warn correct_class
+        warn file_type_warning_message(filename, ext)
         raise TypeError, "#{filename} is not #{name} file"
       when :warning
         warn "are you sure, this is #{name} spreadsheet file?"
-        warn correct_class
+        warn file_type_warning_message(filename, ext)
       when :ignore
         # ignore
       else
@@ -550,6 +544,12 @@ def key_to_string(arr)
 
   private
 
+  def file_type_warning_message(filename, ext)
+    "use #{Roo::CLASS_FOR_EXTENSION.fetch(ext)}.new to handle #{ext} spreadsheet files. This has #{File.extname(filename).downcase}"
+  rescue KeyError
+    raise "unknown file type: #{ext}"
+  end
+
   def find_by_row(row_index)
     row_index += (header_line - 1) if @header_line