Auto-completion for yasnippet and python not working after certain commit

Description :octocat:

Seems the commit 81a931f48bdd6bcca4fdf0a3baab7b4bd7695591 on develop branch made the auto-completion(code completion and yasnippet part) for python. And there will be one python interpreter icon stuck on the dock plane for each *.py file you opened.

Reproduction guide :beetle:

checkout spacemacs to commit 81a931f48bdd6bcca4fdf0a3baab7b4bd7695591
Start Emacs
Open one or two python file.
<>

Observed behaviour: :eyes: :broken_heart: you type some snippet keywords such as main or fd, no auto-completion triggered at all. And if you open two python files, there will be two python interpreter icon(a rocket?) stuck on the dock plane (maybe with jump).

Expected behaviour: :heart: :smile: auto-completion works and no stucked icon on dock plane. auto-completion will work at commit 66afcce4d1512382daba5a15b35df0b2e3ca2734 (previous commit of 81a931f48bdd6bcca4fdf0a3baab7b4bd7695591), but the icon still stucked.

System Info :computer:

OS: darwin
Emacs: 25.3.1
Spacemacs: 0.300.0
Spacemacs branch: temp (rev. 66afcce4)
Graphic display: t
Distribution: spacemacs
Editing style: vim
Completion: helm

Layers:

(ruby ruby-on-rails docker nginx csv javascript helm better-defaults github
  (version-control :variables version-control-diff-tool 'git-gutter+ version-control-global-margin t)
  semantic markdown
  (vinegar :variables vinegar-reuse-dired-buffer t)
  (org :variables org-projectile-file "TODOs.org")
  prodigy search-engine
  (syntax-checking)
  (spell-checking)
  yaml python lua html command-log emacs-lisp emoji fasd deft ranger gtags cscope
  (spacemacs-layouts :variables layouts-enable-autosave t layouts-autosave-delay 300)
  (colors :variables colors-enable-nyan-cat-progress-bar t)
  (git :variables git-magit-status-fullscreen t magit-push-always-verify nil magit-save-repository-buffers 'dontask magit-revert-buffers 'silent magit-refs-show-commit-count 'all magit-revision-show-gravatars nil)
  (ibuffer :variables ibuffer-group-buffers-by 'projects)
  (c-c++ :variables c-c++-default-mode-for-headers 'c++-mode c-c++-enable-clang-support t)
  (auto-completion :variables auto-completion-enable-sort-by-usage t auto-completion-enable-snippets-in-popup t)
  (shell :variables shell-default-position 'full shell-default-shell 'multi-term shell-default-term-shell "/bin/zsh")
  (chinese :variables chinese-enable-fcitx t chinese-enable-youdao-dict t)
  emacs-lisp markdown dash bibtex django pandoc vimscript my)

System configuration features: JPEG RSVG IMAGEMAGICK NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS MODULES

Backtrace :paw_prints:

<<BACKTRACE IF RELEVANT>>

syl20bnr / spacemacs