on error callback

lib/em/mysql.rb

@@ -64,6 +64,8 @@ def notify_readable
     if DisconnectErrors.include? e.message
       @pending << [response, sql, blk]
       return close
+    elsif cb = @opts[:on_error]
+      cb.call(e)
     else
       raise e
     end
@@ -388,6 +390,14 @@ def SQL(query, &blk) SQL.select(query, &blk) end
       }
     end
 
+    should 'fire error callback with exceptions' do
+      SQL.settings.update :on_error => proc{ |e|
+        e.class.should == Mysql::Error
+        done
+      }
+      SQL.select('select 1+ from table'){}
+    end
+
   end
 
 end