vim-patch:8.2.0522: several errors are not tested for (#19901)

Problem:    Several errors are not tested for.
Solution:   Add tests. (Yegappan Lakshmanan, closes vim/vim#5892)
ee4e0c1e9a

Omit Test_range() change: reverted in patch 8.2.0615.
Cherry-pick Test_z_no_space_before_xxx() from patch 8.2.0195.
Cherry-pick Test_reverse_sort_uniq() change from patch 8.2.0183.
Make uniq() error behavior consistent with sort().
Cherry-pick Test_set_ttytype() change from patch 8.1.1826.
Cherry-pick quickfix checks from patch 8.1.2373 to test_preview.vim.
Test_viminfo_error() is applicable.
Cherry-pick E1058 from patch 8.2.0149 and port Test_deep_nest() to Lua.

src/nvim/testdir/test_digraph.vim

@@ -211,6 +211,8 @@ func Test_digraphs()
   call Put_Dig("00")
   call Put_Dig("el")
   call assert_equal(['␀', 'ü', '∞', 'l'], getline(line('.')-3,line('.')))
+  call assert_fails('exe "digraph a\<Esc> 100"', 'E104:')
+  call assert_fails('exe "digraph \<Esc>a 100"', 'E104:')
   call assert_fails('digraph xy z', 'E39:')
   call assert_fails('digraph x', 'E1214:')
   bw!
@@ -491,6 +493,17 @@ func Test_show_digraph_cp1251()
   bwipe!
 endfunc
 
+" Test for error in a keymap file
+func Test_loadkeymap_error()
+  if !has('keymap')
+    return
+  endif
+  call assert_fails('loadkeymap', 'E105:')
+  call writefile(['loadkeymap', 'a'], 'Xkeymap')
+  call assert_fails('source Xkeymap', 'E791:')
+  call delete('Xkeymap')
+endfunc
+
 " Test for the characters displayed on the screen when entering a digraph
 func Test_entering_digraph()
   CheckRunVimInTerminal