Merge pull request #2688 from vim-airline/fix-test

chore: update test

test/themes.vimspec

@@ -4,7 +4,8 @@ Describe themes.vim
     highlight clear Normal
   End
 
-  It should extract correct colors
+  It should extract correct colors with No termguicolors
+    if !exists("+termguicolors")
       call airline#highlighter#reset_hlcache()
       highlight Foo ctermfg=1 ctermbg=2
       let colors = airline#themes#get_highlight('Foo')
@@ -12,6 +13,7 @@ Describe themes.vim
       Assert Equals(colors[1], 'NONE')
       Assert Equals(colors[2], '1')
       Assert Equals(colors[3], '2')
+    endif
   End
 
   if exists("+termguicolors")