`vim`: CtrlP does not work inside other app containers

After a little while fiddling with this, I've come to the conclusion that some `vim` plugins _really_ don't like working inside `pickFolder`.

A key example is [`ctrlp.vim`](https://github.com/ctrlpvim/ctrlp.vim). I installed it inside `~/Documents/.vim/pack/plugins/start` and set my `.vimrc` to:

```vim
" CtrlP
let g:ctrlp_map = ''
let g:ctrlp_cmd = 'CtrlP'
let g:ctrlp_working_path_mode = 'wra'
" Creature comforts
let mapleader=","
set clipboard=unnamed
set mouse=a
syntax on
filetype plugin indent on
" try to set vimwiki to work with the iCloud folder (also doesn't seem to work right)
let g:vimwiki_list = [{'path': '/private/var/mobile/Library/Mobile Documents/iCloud~AsheKube~app~a
-Shell/Documents/vimwiki/', 'syntax': 'markdown', 'ext': '.md'}]
```

I can invoke `ctrlp` fine inside my home directory or any subfolder, but it fails to display a file listing of any kind when used inside `pickFolder`, on any app (I tried iA Writer and Working Copy).