[ruby/logger] require 'logger/errors' just for compat

https://github.com/ruby/logger/commit/255a51dc10

lib/logger.rb

@@ -15,6 +15,7 @@ require 'logger/version'
 require 'logger/formatter'
 require 'logger/log_device'
 require 'logger/severity'
+require 'logger/errors'
 
 # == Description
 #

lib/logger/errors.rb

@@ -1,7 +1,7 @@
+# not used after 1.2.7. just for compat.
 class Logger
   class Error < RuntimeError # :nodoc:
   end
-  # not used after 1.2.7. just for compat.
   class ShiftingError < Error # :nodoc:
   end
 end