我有一个现有的Flask应用程序，并试图添加Flask-Blogging扩展到它。添加扩展引发ImportError: cannot import name FlaskForm时，flask_blogging尝试from flask_wtf import FlaskForm。

Traceback (most recent call last):
  File "run.py", line 11, in <module>
    blog_engine = BloggingEngine(app, sql_storage)
  File "/usr/local/lib/python2.7/dist-packages/flask_blogging/engine.py", line 66, in __init__
    self.init_app(app, storage)
  File "/usr/local/lib/python2.7/dist-packages/flask_blogging/engine.py", line 96, in init_app
    from .views import create_blueprint
  File "/usr/local/lib/python2.7/dist-packages/flask_blogging/views.py", line 11, in <module>
    from flask_blogging.forms import BlogEditor
  File "/usr/local/lib/python2.7/dist-packages/flask_blogging/forms.py", line 1, in <module>
    from flask_wtf import FlaskForm
ImportError: cannot import name FlaskForm

字符串
我使用的是Flask 0.11.1和Flask-WTF 0.12。