test_optparse.rb: skip no_error in backtrace

* test/optparse/test_optparse.rb (TestOptionParser#assert_no_error):
  prefix with assert_ so it will be skipped in backtrace.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40041 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-04-02

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40042 b2dd03c8-39d4-4d8f-98ff-823fe69b080e