patch 8.2.1593: tests do not check the error number properly

Problem:    Tests do not check the error number properly.0
Solution:   Add a colon after the error number. (closes #6869)
diff --git a/src/testdir/test_global.vim b/src/testdir/test_global.vim
index ee4808c..4a01be4 100644
--- a/src/testdir/test_global.vim
+++ b/src/testdir/test_global.vim
@@ -29,7 +29,7 @@
 func Test_nested_global()
   new
   call setline(1, ['nothing', 'found', 'found bad', 'bad'])
-  call assert_fails('g/found/3v/bad/s/^/++/', 'E147')
+  call assert_fails('g/found/3v/bad/s/^/++/', 'E147:')
   g/found/v/bad/s/^/++/
   call assert_equal(['nothing', '++found', 'found bad', 'bad'], getline(1, 4))
   bwipe!