patch 8.2.0670: cannot change window when evaluating 'completefunc'

Problem:    Cannot change window when evaluating 'completefunc'.
Solution:   Make a difference between not changing text or buffers and also
            not changing window.
diff --git a/src/testdir/test_edit.vim b/src/testdir/test_edit.vim
index a9ba31d..f0bf5cc 100644
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -927,7 +927,7 @@
   set completefunc=CompleteFunc
   call setline(1, ['', 'abcd', ''])
   2d
-  call assert_fails("normal 2G$a\<C-X>\<C-U>", 'E565:')
+  call assert_fails("normal 2G$a\<C-X>\<C-U>", 'E578:')
   bwipe!
 endfunc
 
diff --git a/src/testdir/test_ins_complete.vim b/src/testdir/test_ins_complete.vim
index cec4acf..dbea901 100644
--- a/src/testdir/test_ins_complete.vim
+++ b/src/testdir/test_ins_complete.vim
@@ -491,7 +491,7 @@
   endfunc
   set completefunc=CompleteFunc2
   call setline(1, ['', 'abcd', ''])
-  call assert_fails('exe "normal 2G$a\<C-X>\<C-U>"', 'E565:')
+  call assert_fails('exe "normal 2G$a\<C-X>\<C-U>"', 'E578:')
 
   set completefunc&
   delfunc CompleteFunc
diff --git a/src/testdir/test_popup.vim b/src/testdir/test_popup.vim
index 9890377..c7229fc 100644
--- a/src/testdir/test_popup.vim
+++ b/src/testdir/test_popup.vim
@@ -342,7 +342,7 @@
   setlocal completefunc=DummyCompleteOne
   call setline(1, 'one')
   /^one
-  call assert_fails('call feedkeys("A\<C-X>\<C-U>\<C-N>\<Esc>", "x")', 'E565:')
+  call assert_fails('call feedkeys("A\<C-X>\<C-U>\<C-N>\<Esc>", "x")', 'E578:')
   call assert_equal(winid, win_getid())
   call assert_equal('oneDEF', getline(1))
   q!