Improve error message failing to copy proc

Previously, when passing an unshareable proc to a Ractor we would get
the message:

    'Ractor.new': allocator undefined for Proc (TypeError)

With this change we get:

    'Ractor.new': can not copy unshareable object #<Proc:0x00007f1b31713600 test.rb:2> (Ractor::Error)

Which should hopefully be a little clearer about the problem and make it
simpler to debug.

1 files changed, 3 insertions, 3 deletions

diff --git a/bootstraptest/test_ractor.rb b/bootstraptest/test_ractor.rb
index 9242dce7dc..08f9b73c13 100644
--- a/bootstraptest/test_ractor.rb
+++ b/bootstraptest/test_ractor.rb
@@ -507,14 +507,14 @@ assert_equal 'false', %q{
 }
 
 # To copy the object, now Marshal#dump is used
-assert_equal "allocator undefined for Thread", %q{
+assert_match /can not copy unshareable object/, %q{
   obj = Thread.new{}
   begin
     r = Ractor.new obj do |msg|
       msg
     end
-  rescue TypeError => e
-    e.message #=> no _dump_data is defined for class Thread
+  rescue Ractor::Error => e
+    e.message
   else
     'ng'
   end