Error loading custom_init.vim
Thanks for SpaceVim, it's amazing.

## Expected behavior, english is required
Load `custom_init.vim` using `init.toml`

## The reproduce ways from Vim starting (Required!)
```
mkdir -p ~/.SpaceVim.d/autoload
touch ~/.SpaceVim.d/autoload/custom_init.vim
echo "set mouse=r" > ~/.SpaceVim.d/autoload/custom_init.vim

# Add this line to ~/.SpaceVim.d/init.toml in [options] session
bootstrap_after  = "custom_init#after"
```

## Debug info

Please press <kbd>SPC h I</kbd>, debug info will be put into clipboard, then paste all content below.
```
<!-- please remove the issue template when request for a feature -->
## Expected behavior, english is recommend

## Environment Information

- OS: mac
- vim version: 8.2(1-850, 1972
Compiled by root@apple.com
Normal version without GUI.  Features included (+) or not (-):
+acl               +cryptv            +fork()            +modify_fname      +persistent_undo   +syntax            +visualextra
-arabic            +cscope            -gettext           +mouse             +popupwin          +tag_binary        +viminfo
+autocmd           +cursorbind        -hangul_input      -mouseshape        +postscript        -tag_old_static    +vreplace
+autochdir         +cursorshape       +iconv             -mouse_dec         +printer           -tag_any_white     +wildignore
-autoservername    +dialog_con        +insert_expand     -mouse_gpm         -profile           -tcl               +wildmenu
-balloon_eval      +diff              -ipv6              -mouse_jsbterm     +python/dyn        -termguicolors     +windows
-balloon_eval_term +digraphs          +job               -mouse_netterm     -python3           +terminal          +writebackup
-browse            -dnd               +jumplist          +mouse_sgr         +quickfix          +terminfo          -X11
+builtin_terms     -ebcdic            -keymap            -mouse_sysmouse    +reltime           +termresponse      -xfontset
+byte_offset       -emacs_tags        +lambda            -mouse_urxvt       -rightleft         +textobjects       -xim
+channel           +eval              -langmap           +mouse_xterm       +ruby/dyn          +textprop          -xpm
+cindent           +ex_extra          +libcall           +multi_byte        +scrollbind        +timers            -xsmp
-clientserver      +extra_search      +linebreak         +multi_lang        +signs             +title             -xterm_clipboard
+clipboard         -farsi             +lispindent        -mzscheme          +smartindent       -toolbar           -xterm_save
+cmdline_compl     +file_in_path      +listcmds          +netbeans_intg     -sound             +user_commands     
+cmdline_hist      +find_in_path      +localmap          +num64             +spell             -vartabs           
+cmdline_info      +float             -lua               +packages          +startuptime       +vertsplit         
+comments          +folding           +menu              +path_extra        +statusline        +virtualedit       
-conceal           -footer            +mksession         -perl              -sun_workshop      +visual            
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
  fall-back for $VIM: "/usr/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H   -DMACOS_X_UNIX  -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1      
Linking: gcc   -L/usr/local/lib -o vim        -lm -lncurses  -liconv -framework Cocoa           )
- neovim version: -
- SpaceVim version: 1.7.0-dev
- SpaceVim status: da5e3205


```
On branch master
Your branch is up to date with 'origin/master'.

nothing to commit, working tree clean
```

## The reproduce ways from Vim starting (Required!)

## Output of the `:SPDebugInfo!`

<details><summary> SpaceVim debug information </summary>

### SpaceVim options :

```toml
  auto_disable_touchpad = 1
  autocomplete_method = 'completor'
  autocomplete_parens = 1
  bootstrap_after = 'custom_init#after'
  buffer_index_type = 4
  checkinstall = 1
  colorscheme = 'vim-material'
  colorscheme_bg = 'dark'
  colorscheme_default = 'desert'
  commandline_prompt = '➭'
  custom_color_palette = []
  custom_plugins = [['hzchirs/vim-material', {'repo': 'hzchirs/vim-material', 'merged': 0, 'overwrite': 1}], ['junegunn/vim-easy-align', {'repo': 'junegunn/vim-easy-align', 'merged': 0, 'overwrite': 1}], ['hashivim/vim-vagrant', {'repo': 'hashivim/vim-vagrant', 'merged': 0, 'overwrite': 1}], ['hashivim/vim-terraform', {'repo': 'hashivim/vim-terraform', 'merged': 0, 'overwrite': 1}], ['hashivim/vim-vaultproject', {'repo': 'hashivim/vim-vaultproject', 'merged': 0, 'overwrite': 1}], ['pearofducks/ansible-vim', {'repo': 'pearofducks/ansible-vim', 'merged': 0, 'overwrite': 1}]]
  data_dir = '/Users/vitorjr/.cache/'
  debug_level = 1
  default_custom_leader = '<Space>'
  default_indent = 2
  disabled_plugins = []
  enable_bepo_layout = 0
  enable_cursorcolumn = 0
  enable_cursorline = 1
  enable_debug = 0
  enable_googlesuggest = 0
  enable_guicolors = 1
  enable_javacomplete2_py = 0
  enable_key_frequency = 0
  enable_language_specific_leader = 1
  enable_neocomplcache = 0
  enable_os_fileformat_icon = 0
  enable_powerline_fonts = 1
  enable_projects_cache = 1
  enable_statusline_bfpath = 0
  enable_statusline_mode = 1
  enable_statusline_tag = 1
  enable_tabline_filetype_icon = 1
  enable_tabline_ft_icon = 0
  enable_vimfiler_filetypeicon = 0
  enable_vimfiler_gitstatus = 0
  enable_vimfiler_welcome = 1
  enable_ycm = 0
  error_symbol = '✖'
  escape_key_binding = 'jk'
  expand_tab = 1
  filemanager = 'nerdtree'
  filetree_direction = 'right'
  filetype_icons = {}
  force_global_config = 0
  gitcommit_issue_icon = ''
  gitcommit_pr_icon = ''
  github_username = ''
  guifont = ''
  hiddenfileinfo = 1
  home_files_number = 6
  hosts_url = 'https://raw.githubusercontent.com/racaljk/hosts/master/hosts'
  info_symbol = 'ⓘ'
  keep_server_alive = 1
  language = ''
  leader_guide_default_group_name = ''
  leader_guide_flatten = 1
  leader_guide_hspace = 5
  leader_guide_max_size = 0
  leader_guide_position = 'botright'
  leader_guide_run_map_on_popup = 1
  leader_guide_sort_horizontal = 0
  leader_guide_submode_mappings = {'<C-C>': 'win_close'}
  leader_guide_vertical = 0
  lint_engine = 'neomake'
  lint_on_save = 1
  lint_on_the_fly = 0
  max_column = 120
  plugin_bundle_dir = '/Users/vitorjr/.cache/vimfiles/'
  plugin_manager = 'dein'
  plugin_manager_processes = 16
  plugin_name = 'deoplete-zsh'
  project_rooter_automatically = 1
  project_rooter_outermost = 1
  project_rooter_patterns = ['.git/', '_darcs/', '.hg/', '.bzr/', '.svn/', '.SpaceVim.d/']
  projects_cache_num = 20
  realtime_leader_guide = 1
  relativenumber = 1
  search_tools = ['rg', 'ag', 'pt', 'ack', 'grep', 'findstr', 'git']
  sidebar_direction = ''
  sidebar_width = 30
  smartcloseignoreft = ['tagbar', 'vimfiler', 'defx', 'SpaceVimRunner', 'SpaceVimREPL', 'SpaceVimQuickFix', 'HelpDescribe', 'VebuggerShell', 'VebuggerTerminal', 'SpaceVimTabsManager']
  smartcloseignorewin = ['__Tagbar__', 'vimfiler:default']
  snippet_engine = 'neosnippet'
  src_root = 'E:\sources\'
  statusline_iseparator = 'arrow'
  statusline_left_sections = ['winnr', 'filename', 'major mode', 'search count', 'syntax checking', 'minor mode lighters', 'vcs', 'hunks']
  statusline_right_sections = ['fileformat', 'cursorpos', 'percentage']
  statusline_separator = 'arrow'
  statusline_unicode_symbols = 1
  terminal_cursor_shape = 2
  todo_labels = ['@fixme', '@question', '@todo', '@idea']
  update_retry_cnt = 3
  version = '1.7.0-dev'
  vim_help_language = 'en'
  vimcompatible = 0
  warning_symbol = '⚠'
  wildignore = '*/tmp/*,*.so,*.swp,*.zip,*.class,tags,*.jpg,*.ttf,*.TTF,*.png,*/target/*,.git,.svn,.hg,.DS_Store,*.svg'
  windows_index_type = 3
  windows_leader = 's'
  windows_smartclose = 'q'
```


### SpaceVim layers :

```toml
[[layers]]
  name="autocomplete"
  auto_completion_return_key_behavior='complete'
  auto_completion_tab_key_behavior='smart'
[[layers]]
  name="checkers"
[[layers]]
  name="format"
[[layers]]
  name="edit"
[[layers]]
  name="ui"
[[layers]]
  name="core"
[[layers]]
  name="core#banner"
[[layers]]
  name="core#statusline"
[[layers]]
  name="core#tabline"
[[layers]]
  name="shell"
  default_position='top'
  default_height=30
[[layers]]
  name="VersionControl"
[[layers]]
  name="git"
[[layers]]
  name="lang#elixir"
[[layers]]
  name="lang#erlang"
[[layers]]
  name="lang#ruby"
[[layers]]
  name="lang#sh"
```


### SpaceVim Health checking :

SpaceVim clipboard support check report:
Checking +clipboard:
      SUCCEED!
SpaceVim environment check report:
Current progpath: vi(vi)
version: 802
OS: mac
[shell, shellcmdflag, shellslash]: ['/bin/zsh', '-c', 0]
SpaceVim lua support check report:
Checking +lua:
      Failed : to support +lua, you need recompile your vim with +lua support.
SpaceVim python support check report:
Checking +python3:
      Failed : to support +python3, Please install vim-gtk, or build from sources.
Checking +python:
      SUCCEED!

### SpaceVim runtime log :

```log
[ SpaceVim ] : logger file  does not exists, only log for current process will be shown!
[ SpaceVim ] [17:51:33] [ Info ] Startup with argv: ['teste']
[ SpaceVim ] [17:51:33] [ Info ] Can not find project local config, start loading global config
[ SpaceVim ] [17:51:33] [ Info ] global_dir is: /Users/vitorjr/.SpaceVim.d/
[ SpaceVim ] [17:51:33] [ Info ] start to apply config [glob]
[ SpaceVim ] [17:51:33] [ Info ] the func has been added to mode:syntax-checking
[ SpaceVim ] [17:51:33] [ Info ] the func has been added to mode:spell-checking
[   rooter ] [17:51:33] [ Info ] Load projects cache from: /Users/vitorjr/.cache/SpaceVim/projects.json
[   rooter ] [17:51:34] [ Info ] Start to find root for: /Users/vitorjr/Downloads/teste
[   rooter ] [17:51:34] [ Info ] buffer name: teste
[   rooter ] [17:51:34] [ Info ] same as current directory, no need to change.
[ SpaceVim ] [17:51:34] [ Error ] failed to call bootstrap_after function: custom_init#after
[ SpaceVim ] [17:51:34] [ Error ]        exception: Vim(call):E117: Unknown function: custom_init#after
[ SpaceVim ] [17:51:34] [ Error ]        throwpoint: function SpaceVim#autocmds#VimEnter, line 34
[   rooter ] [17:51:34] [ Info ] buffer name: teste
[   rooter ] [17:51:34] [ Info ] same as current directory, no need to change.
[   rooter ] [17:51:35] [ Info ] Start to find root for: /private/var/folders/5q/qbppj_gx30s7f4z_535ddh_m0000gn/T/v3HGzBA/1/issue_report.md
[   rooter ] [17:51:35] [ Info ] buffer name: /var/folders/5q/qbppj_gx30s7f4z_535ddh_m0000gn/T/v3HGzBA/1/issue_report.md
[   rooter ] [17:51:35] [ Info ] same as current directory, no need to change.
```
</details>

## Screenshots

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[![asciicast](https://asciinema.org/a/d69gmn8glqGOZfjFasgnR1qUX.svg)](https://asciinema.org/a/d69gmn8glqGOZfjFasgnR1qUX)