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_fail.vim b/src/testdir/test_terminal_fail.vim
index aad4b98..d010c3b 100644
--- a/src/testdir/test_terminal_fail.vim
+++ b/src/testdir/test_terminal_fail.vim
@@ -3,7 +3,7 @@
 " freed.  Since the process exists right away it's not a real leak.
 
 if !has('terminal')
-  finish
+  throw 'Skipped, terminal feature missing'
 endif
 
 source shared.vim