text: Title: TypeError: <flask_script.commands.Shell object at 0x0000000004D13C88>: 'dict' object is not callable
  Body: In windows 7 with Pycharm, 
  For Chapter 5.10 "**Integration with the Python Shell**",  register make_context:
  ‘def make_shell_context():     
        return dict(app=app,db=db,User=User,Role=Role)    
  manager.add_command("shell", Shell(make_context=make_shell_context()))‘
  
  when i run command "python app/welcome.py shell" in cmd or terminal in Pycharm, this error occurs:
  
  (venv) C:\Users\biont.liu\PycharmProjects\flasky>python app/welcome.py shell
  Traceback (most recent call last):
    File "app/welcome.py", line 106, in <module>
       manager.run()
    File "C:\Users\biont.liu\PycharmProjects\flasky\venv\lib\site-packages\flask_script\__init__.py", line 417, in run
      result = self.handle(argv[0], argv[1:])
    File "C:\Users\biont.liu\PycharmProjects\flasky\venv\lib\site-packages\flask_script\__init__.py", line 386, in handle
      res = handle(*args, **config)
    File "C:\Users\biont.liu\PycharmProjects\flasky\venv\lib\site-packages\flask_script\commands.py", line 216, in __call__
      return self.run(*args, **kwargs)
    File "C:\Users\biont.liu\PycharmProjects\flasky\venv\lib\site-packages\flask_script\commands.py", line 304, in run
      context = self.get_context()
    File "C:\Users\biont.liu\PycharmProjects\flasky\venv\lib\site-packages\flask_script\commands.py", line 293, in get_context
      return self.make_context()
  TypeError: <flask_script.commands.Shell object at 0x0000000004D13C88>: 'dict' object is not callable
  
  **when i return list/strings in make_shell_context(), it prompts "'list'/'str' object is not callable.”**
  
  
  **Further step:**
  1. For command "python app/welcome.py db init":
  Creating directory C:\Users\biont.liu\PycharmProjects\flasky\migrations ... done
  Creating directory C:\Users\biont.liu\PycharmProjects\flasky\migrations\versions ... done
  Generating C:\Users\biont.liu\PycharmProjects\flasky\migrations\alembic.ini ... done
  Generating C:\Users\biont.liu\PycharmProjects\flasky\migrations\env.py ... done
  Generating C:\Users\biont.liu\PycharmProjects\flasky\migrations\README ... done
  Generating C:\Users\biont.liu\PycharmProjects\flasky\migrations\script.py.mako ... done
  Please edit configuration/connection/logging settings in 'C:\\Users\\biont.liu\\PycharmProjects\\flasky\\migrations\\alembic.ini' before proceeding.
  
  2. For command "python app/welcome.py db migrate -m "initial migration":
  INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
  INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
  INFO  [alembic.env] No changes in schema detected.
  
  3. For command "python app/welcome.py db upgrade":
  INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
  INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
  