try to get rid of annoying deprecation message
try to get rid of annoying deprecation message

 warning: Comparable#== will no more rescue exceptions of #<=> in the next release.
/Users/homanchou/.rvm/gems/ruby-2.2.0@sb/gems/xml-mapping-0.8.1/lib/xml/mapping/base.rb:376: warning: Return nil in #<=> if the comparison is inappropriate or avoid such comparison.
Sellbrite/ebay,Sellbrite/ebay