Use has('gui_running') instead of has('gui')

doc/ale.txt

@@ -1806,7 +1806,7 @@ g:ale_pattern_options_enabled                   *g:ale_pattern_options_enabled*
 g:ale_popup_menu_enabled                             *g:ale_popup_menu_enabled*
 
   Type: |Number|
-  Default: `has('gui')`
+  Default: `has('gui_running')`
 
   When this option is set to `1`, ALE will show code actions and rename
   capabilities in the right click mouse menu when there's a LSP server or

plugin/ale.vim

@@ -159,7 +159,7 @@ let g:ale_python_auto_pipenv = get(g:, 'ale_python_auto_pipenv', 0)
 let g:ale_go_go111module = get(g:, 'ale_go_go111module', '')
 
 " If 1, enable a popup menu for commands.
-let g:ale_popup_menu_enabled = get(g:, 'ale_popup_menu_enabled', has('gui'))
+let g:ale_popup_menu_enabled = get(g:, 'ale_popup_menu_enabled', has('gui_running'))
 
 if g:ale_set_balloons is 1 || g:ale_set_balloons is# 'hover'
     call ale#balloon#Enable()

test/test_lint_on_enter_when_file_changed.vader

@@ -35,7 +35,7 @@ After:
 Execute(The file changed event function should set b:ale_file_changed):
   let g:ale_lint_on_enter = 0
 
-  if has('gui')
+  if has('gui_running')
     new
   else
     e test