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_perl.vim b/src/testdir/test_perl.vim
index e24c04f..d38fc07 100644
--- a/src/testdir/test_perl.vim
+++ b/src/testdir/test_perl.vim
@@ -1,7 +1,7 @@
 " Tests for Perl interface
 
 if !has('perl')
-  finish
+  throw 'Skipped, perl feature missing'
 end
 
 " FIXME: RunTest don't see any error when Perl abort...