Add key binding SPC e e (#2507)

autoload/SpaceVim/layers/checkers.vim

@@ -91,6 +91,9 @@ function! SpaceVim#layers#checkers#config() abort
   call SpaceVim#mapping#space#def('nnoremap', ['t', 's'], 'call call('
         \ . string(s:_function('s:toggle_syntax_checker')) . ', [])',
         \ 'toggle syntax checker', 1)
+  call SpaceVim#mapping#space#def('nnoremap', ['e', 'e'], 'call call('
+        \ . string(s:_function('s:explain_the_error')) . ', [])',
+        \ 'explain the error', 1)
   augroup SpaceVim_layer_checker
     autocmd!
     if g:spacevim_enable_neomake
@@ -221,6 +224,28 @@ function! s:toggle_syntax_checker() abort
   verbose NeomakeToggle
 endfunction
 
+
+function! s:explain_the_error() abort
+  if g:spacevim_enable_neomake
+    try
+      let message = neomake#GetCurrentErrorMsg()
+    catch /^Vim\%((\a\+)\)\=:E117/
+      let message = ''
+    endtry
+  elseif g:spacevim_enable_ale
+    try
+      let message = neomake#GetCurrentErrorMsg()
+    catch /^Vim\%((\a\+)\)\=:E117/
+      let message = ''
+    endtry
+  endif
+  if !empty(message)
+    echo message
+  else
+    echo 'no error message at this point!'
+  endif
+endfunction
+
 function! s:error_transient_state() abort
   if g:spacevim_enable_neomake
     let num_errors = neomake#statusline#LoclistCounts()