Combine backtrace from async execution with the location of its rising

Author: pitr-ch

lib/concurrent/edge/promises.rb

@@ -962,7 +962,9 @@ def exception(*args)
         if reason.size > 1
           Concurrent::MultipleErrors.new reason
         else
-          reason[0].exception(*args)
+          ex = reason[0].exception(*args)
+          ex.set_backtrace ex.backtrace + caller
+          ex
         end
       end