patch 8.0.0663: unexpected error message only when 'verbose' is set

Problem:    Giving an error message only when 'verbose' set is unexpected.
Solution:   Give a warning message instead.
diff --git a/src/testdir/test_vimscript.vim b/src/testdir/test_vimscript.vim
index c0736f2..13b32cd 100644
--- a/src/testdir/test_vimscript.vim
+++ b/src/testdir/test_vimscript.vim
@@ -1381,10 +1381,12 @@
 
     set verbose=1
     exe "func Xtest()\necho 'hello'\nendfunc \" garbage"
+    call assert_notmatch('W22:', split(execute('1messages'), "\n")[0])
     call assert_true(exists('*Xtest'))
     delfunc Xtest
 
-    call assert_fails("func Xtest()\necho 'hello'\nendfunc garbage", 'E946')
+    exe "func Xtest()\necho 'hello'\nendfunc garbage"
+    call assert_match('W22:', split(execute('1messages'), "\n")[0])
     call assert_true(exists('*Xtest'))
     delfunc Xtest
     set verbose=0