revises some details in the previous explain patch

activerecord/lib/active_record/explain.rb

@@ -1,5 +1,5 @@
 module ActiveRecord
-  module Explain # :nodoc
+  module Explain # :nodoc:
     # logging_query_plan calls could appear nested in the call stack. In
     # particular this happens when a relation fetches its records, since
     # that results in find_by_sql calls downwards.
@@ -31,7 +31,7 @@ module ActiveRecord
 
     # SCHEMA queries cannot be EXPLAINed, also we do not want to run EXPLAIN on
     # our own EXPLAINs now matter how loopingly beautiful that would be.
-    SKIP_EXPLAIN_FOR = %(SCHEMA EXPLAIN)
+    SKIP_EXPLAIN_FOR = %w(SCHEMA EXPLAIN)
     def ignore_explain_notification?(payload)
       payload[:exception] || SKIP_EXPLAIN_FOR.include?(payload[:name])
     end

activerecord/lib/active_record/relation.rb

@@ -155,7 +155,7 @@ module ActiveRecord
     # Please see further details in the
     # {Active Record Query Interface guide}[http://edgeguides.rubyonrails.org/active_record_querying.html#running-explain].
    def explain
-      results, sqls, binds = collecting_sqls_for_explain { exec_query }
+      _, sqls, binds = collecting_sqls_for_explain { exec_query }
       exec_explain(sqls, binds)
     end
 

railties/CHANGELOG.md

@@ -5,7 +5,7 @@
     configuration files. With a value of 0.5 in development.rb, and commented
     out in production.rb. No mention in test.rb. *fxn*
 
-*   Display mounted engine's routes in `rake routes`. *Piotr Sarnacki*
+*   Add DebugExceptions middleware which contains features extracted from ShowExceptions middleware *José Valim*
 
 *   Display mounted engine's routes in `rake routes` *Piotr Sarnacki*