Handle exception error message differences.

Author: ioquatix

test/io.rb

@@ -115,7 +115,7 @@
 			read_task = Async do
 				expect do
 					r.read(5)
-				end.to raise_exception(IOError, message: be =~ /stream closed/)
+				end.to raise_exception(IOError, message: be =~ /closed/)
 			end
 
 			close_task = Async do
@@ -188,7 +188,7 @@
 
 			expect do
 				read_thread.join
-			end.to raise_exception(IOError, message: be =~ /stream closed/)
+			end.to raise_exception(IOError, message: be =~ /closed/)
 		end
 
 		it "can interrupt reading fiber in a new thread when closing from a fiber" do