参照《Flask Web 开发》书中方法更新数据库出错如何解

学习到《Flask Web开发》第八章时，运行代码报错。后来意识到User表中新增了一列，应该更新数据库，执行

python manage.py db migrate -m "initial migration"

结果报错：alembic.util.exc.CommandError: Target database is not up to date.

这种错误先前没有遇到过，网上找了一下也不理解。

相关代码app/models.py:

from . import db
from werkzeug.security import generate_password_hash, check_password_hash
from flask_login import UserMixin
from . import login_manager
from itsdangerous import TimedJSONWebSignatureSerializer as Serializer
from flask import current_app


@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))

class Role(db.Model):
    __tablename__ = 'roles'
    id = db.Column(db.Integer, primary_key = True)
    name = db.Column(db.String(64), unique = True)
    users = db.relationship('User', backref = 'role', lazy = 'dynamic')
    
    def __repr__(self):
        return '<Role %r>' % self.name
        
class User(UserMixin, db.Model):
    __tablename__ = 'users'
    id = db.Column(db.Integer, primary_key = True)
    email = db.Column(db.String(64), unique=True, index=True)
    username = db.Column(db.String(64), unique = True, index = True)
    role_id = db.Column(db.Integer, db.ForeignKey('roles.id'))
    password_hash = db.Column(db.String(128))
    confirmed = db.Column(db.Boolean, default=False)
    
    @property
    def password(self):
        raise AttributeError('password is not a readable attribute')
    
    @password.setter
    def password(self, password):
        self.password_hash = generate_password_hash(password)
    
    def verify_password(self, password):
        return check_password_hash(self.password_hash, password)
    
    def __repr__(self):
        return '<User %r>' % self.username

    def generate_confirmation_token(self, expiration=3600):
        s = Serializer(current_app.config['SECRET_KEY'], expiration)
        return s.dump({'confirm': self.id})

    def confirm(self, token):
        s = Serializer(current_app.config['SECRET_KEY'])
        try:
            data = s.loads(token)
        except:
            return False
        if data.get('confirm') != self.id:
            return False
        self.confirmed = True
        db.session.add(self)
        return True

求指导！！！

确定 Google 过 ?
删除了migrations文件夹里一个版本后能正常更新了。

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