Ruby

IO#readpartial rejects bad args

Sometimes a sleepy developer will want to swap read_nonblock
for readpartial forget to remove "exception: false"

• io.c (io_getpartial): remove unused kwarg from template
• test/ruby/test_io.rb (test_readpartial_bad_args): new
  [Bug #11885]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53329 b2dd03c8-39d4-4d8f-98ff-823fe69b080e