patch 8.1.1524: tests are silently skipped

Problem:    Tests are silently skipped.
Solution:   Throw an exception for skipped tests in more places.
diff --git a/src/testdir/test_terminal.vim b/src/testdir/test_terminal.vim
index 5fab975..09c050a 100644
--- a/src/testdir/test_terminal.vim
+++ b/src/testdir/test_terminal.vim
@@ -1,7 +1,7 @@
 " Tests for the terminal window.
 
 if !has('terminal')
-  finish
+  throw 'Skipped, terminal feature missing'
 endif
 
 source shared.vim