max_length 属性

错误:漏掉了 max_length  属性 

ERRORS:
users.UserProfile.image: (fields.E210) Cannot use ImageField because Pillow is not installed.
HINT: Get Pillow at https://pypi.python.org/pypi/Pillow or run command "pip install Pillow".

image字段需要依赖另外一个库，pillow

ValueError: Dependency on app with no migrations: users

先要做 migrations