Django2.1.3框架中(fields.E300)和(fields.E307)报错处理

        使用Django框架创建了Web项目，修改了模型models.py之后，执行数据库迁移操作，出现如下报错：

models.py内容如下：

from django.db import models
from django.contrib.auth.models import User


# Create your models here.

class Asset(models.Model):
    """所有资产的共有数据表"""
    assets_type_choice = (
        ('Server', '服务器'),
        ('NetworkDevice', '网络设备'),
        ('StorageDevice', '存储设备'),
        ('SecurityDevice', '安全设备'),
        ('Software', '软件资产'),
    )

    asset_status = (
        (0, '在线'),
        (1, '下线'),
        (2, '未知'),
        (3, '故障'),
        (4, '备用'),
    )
    asset_type = models.CharField(choices=assets_type_choice, max_length=64, default='Server', verbose_name='资产类型')
    name = models.CharField(max_length=64, unique=True, verbose_name='资产名称')  # 不可重复
    sn = models.CharField(max_length=128, unique=True, verbose_name='资产序列号')  # 不可重复
    business_unit = models.ForeignKey('BusinessUnit', null=True, blank=True, verbose_name='所属业务线',
                                      on_delete=models.CASCADE)
    status = models.CharField(choices=asset_status, max_length=64, default=0, verbose_name='设备状态')
    manufacturer = models.ForeignKey('Manufacturer', null=True, blank=True, verbose_name='设备制造商',
                                     on_delete=models.CASCADE)
    manage_ip = models.GenericIPAddressField(null=True, blank=True, verbose_name='管理IP')
    tags = models.ManyToManyField('Tag', blank=True, verbose_name='标签')
    admin = models.ForeignKey(User, null=True, blank=True, verbose_name='资产管理员', related_name='admin',
                              on_delete=models.CASCADE)
    idc = models.ForeignKey('IDC', null=True, blank=True, verbose_name='所在数据中心', on_delete=models.CASCADE)
    contract = models.ForeignKey('Contract', null=True, blank=True, verbose_name='合同', on_delete=models.CASCADE)
    purchase_date = models.DateField(null=True, blank=True, verbose_name='购买日期')
    expire_date = models.DateField(null=True, blank=True, verbose_name='过保日期')
    price = models.FloatField(null=True, blank=True, verbose_name='价格')
    approved_by = models.ForeignKey(User, null=True, blank=True, verbose_name='批准人',
                                    related_name='approved_by',
                                    on_delete=models.CASCADE)
    memo = models.TextField(null=True, blank=True, verbose_name='备注')
    c_time = models.DateTimeField(auto_now_add=True, verbose_name='批准日期')
    m_time = models.DateTimeField(auto_now=True, verbose_name='更新日期')

    def __str__(self):
        return '<%s> %s' % (self.get_asset_type_display(), self.name)

    class Meta:
        verbose_name = '资产总表'
        verbose_name_plural = verbose_name
        ordering = ['-c_time']


class Server(models.Model):
    """服务器设备"""
    sub_asset_type_choice = (
        (0, 'PC服务器'),
        (1, '刀片机'),
        (2, '小型机'),
    )

    created_by_choice = (
        ('auto', '自动添加'),
        ('manual', '手工录入'),
    )

    asset = models.OneToOneField('Asset', on_delete=models.CASCADE)  # 非常关键的一对一关联！
    sub_asset_type = models.SmallIntegerField(choices=sub_asset_type_choice, default=0, verbose_name="服务器类型")
    created_by = models.CharField(choices=created_by_choice, max_length=32, default='auto', verbose_name="添加方式")
    hosted_on = models.ForeignKey('self', related_name='hosted_on_server',
                                  blank=True, null=True, verbose_name="宿主机", on_delete=models.CASCADE)  # 虚拟机专用字段
    model = models.CharField(max_length=128, null=True, blank=True, verbose_name='服务器型号')
    raid_type = models.CharField(max_length=512, blank=True, null=True, verbose_name='Raid类型')

    os_type = models.CharField('操作系统类型', max_length=64, blank=True, null=True)
    os_distribution = models.CharField('发行版本', max_length=64, blank=True, null=True)
    os_release = models.CharField('操作系统版本', max_length=64, blank=True, null=True)

    def __str__(self):
        return '%s--%s--%s <sn:%s>' % (self.asset.name, self.get_sub_asset_type_display(), self.model, self.asset.sn)

    class Meta:
        verbose_name = '服务器'
        verbose_name_plural = "服务器"


class SecurityDevice(models.Model):
    """安全设备"""
    sub_asset_type_choice = (
        (0, '防火墙'),
        (1, '入侵检测设备'),
        (2, '互联网网关'),
        (4, '运维审计系统'),
    )

    asset = models.OneToOneField('Asset', on_delete=models.CASCADE)
    sub_asset_type = models.SmallIntegerField(choices=sub_asset_type_choice, default=0, verbose_name="安全设备类型")

    def __str__(self):
        return self.asset.name + "--" + self.get_sub_asset_type_display() + " id:%s" % self.id

    class Meta:
        verbose_name = '安全设备'
        verbose_name_plural = "安全设备"


class StorageDevice(models.Model):
    """存储设备"""
    sub_asset_type_choice = (
        (0, '磁盘阵列'),
        (1, '网络存储器'),
        (2, '磁带库'),
        (4, '磁带机'),
    )

    asset = models.OneToOneField('Asset', on_delete=models.CASCADE)
    sub_asset_type = models.SmallIntegerField(choices=sub_asset_type_choice, default=0, verbose_name="存储设备类型")

    def __str__(self):
        return self.asset.name + "--" + self.get_sub_asset_type_display() + " id:%s" % self.id

    class Meta:
        verbose_name = '存储设备'
        verbose_name_plural = "存储设备"


class NetworkDevice(models.Model):
    """网络设备"""
    sub_asset_type_choice = (
        (0, '路由器'),
        (1, '交换机'),
        (2, '负载均衡'),
        (4, 'VPN设备'),
    )

    asset = models.OneToOneField('Asset', on_delete=models.CASCADE)
    sub_asset_type = models.SmallIntegerField(choices=sub_asset_type_choice, default=0, verbose_name="网络设备类型")

    vlan_ip = models.GenericIPAddressField(blank=True, null=True, verbose_name="VLanIP")
    intranet_ip = models.GenericIPAddressField(blank=True, null=True, verbose_name="内网IP")

    model = models.CharField(max_length=128, null=True, blank=True, verbose_name="网络设备型号")
    firmware = models.CharField(max_length=128, blank=True, null=True, verbose_name="设备固件版本")
    port_num = models.SmallIntegerField(null=True, blank=True, verbose_name="端口个数")
    device_detail = models.TextField(null=True, blank=True, verbose_name="详细配置")

    def __str__(self):
        return '%s--%s--%s <sn:%s>' % (self.asset.name, self.get_sub_asset_type_display(), self.model, self.asset.sn)

    class Meta:
        verbose_name = '网络设备'
        verbose_name_plural = "网络设备"


class Software(models.Model):
    """
    只保存付费购买的软件
    """
    sub_asset_type_choice = (
        (0, '操作系统'),
        (1, '办公开发软件'),
        (2, '业务软件'),
    )

    sub_asset_type = models.SmallIntegerField(choices=sub_asset_type_choice, default=0, verbose_name="软件类型")
    license_num = models.IntegerField(default=1, verbose_name="授权数量")
    version = models.CharField(max_length=64, unique=True, help_text='例如: CentOS release 6.7 (Final)',
                               verbose_name='软件/系统版本')

    def __str__(self):
        return '%s--%s' % (self.get_sub_asset_type_display(), self.version)

    class Meta:
        verbose_name = '软件/系统'
        verbose_name_plural = "软件/系统"


class IDC(models.Model):
    """机房"""
    name = models.CharField(max_length=64, unique=True, verbose_name="机房名称")
    memo = models.CharField(max_length=128, blank=True, null=True, verbose_name='备注')

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = '机房'
        verbose_name_plural = "机房"


class Manufacturer(models.Model):
    """厂商"""

    name = models.CharField('厂商名称', max_length=64, unique=True)
    telephone = models.CharField('支持电话', max_length=30, blank=True, null=True)
    memo = models.CharField('备注', max_length=128, blank=True, null=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = '厂商'
        verbose_name_plural = "厂商"


class BusinessUnit(models.Model):
    """业务线"""

    parent_unit = models.ForeignKey('self', blank=True, null=True, related_name='parent_level',
                                    on_delete=models.CASCADE)
    name = models.CharField('业务线', max_length=64, unique=True)
    memo = models.CharField('备注', max_length=64, blank=True, null=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = '业务线'
        verbose_name_plural = "业务线"


class Contract(models.Model):
    """合同"""

    sn = models.CharField('合同号', max_length=128, unique=True)
    name = models.CharField('合同名称', max_length=64)
    memo = models.TextField('备注', blank=True, null=True)
    price = models.IntegerField('合同金额')
    detail = models.TextField('合同详细', blank=True, null=True)
    start_day = models.DateField('开始日期', blank=True, null=True)
    end_day = models.DateField('失效日期', blank=True, null=True)
    license_num = models.IntegerField('license数量', blank=True, null=True)
    c_day = models.DateField('创建日期', auto_now_add=True)
    m_day = models.DateField('修改日期', auto_now=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = '合同'
        verbose_name_plural = "合同"


class Tag(models.Model):
    """标签"""
    name = models.CharField('标签名', max_length=32, unique=True)
    c_day = models.DateField('创建日期', auto_now_add=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = '标签'
        verbose_name_plural = "标签"


class Disk(models.Model):
    """存储设备"""

    disk_interface_type_choice = (
        ('SATA', 'SATA'),
        ('SAS', 'SAS'),
        ('SCSI', 'SCSI'),
        ('SSD', 'SSD'),
        ('unknown', 'unknown'),
    )

    asset = models.ForeignKey('Asset', on_delete=models.CASCADE)
    sn = models.CharField('硬盘SN号', max_length=128)
    slot = models.CharField('所在插槽位', max_length=64, blank=True, null=True)
    model = models.CharField('磁盘型号', max_length=128, blank=True, null=True)
    manufacturer = models.CharField('磁盘制造商', max_length=128, blank=True, null=True)
    capacity = models.FloatField('磁盘容量(GB)', blank=True, null=True)
    interface_type = models.CharField('接口类型', max_length=16, choices=disk_interface_type_choice, default='unknown')

    def __str__(self):
        return '%s:  %s:  %s:  %sGB' % (self.asset.name, self.model, self.slot, self.capacity)

    class Meta:
        verbose_name = '硬盘'
        verbose_name_plural = "硬盘"
        unique_together = ('asset', 'sn')


class EventLog(models.Model):
    """
    日志.
    在关联对象被删除的时候，不能一并删除，需保留日志。
    因此，on_delete=models.SET_NULL
    """

    name = models.CharField('事件名称', max_length=128)
    event_type_choice = (
        (0, '其它'),
        (1, '硬件变更'),
        (2, '新增配件'),
        (3, '设备下线'),
        (4, '设备上线'),
        (5, '定期维护'),
        (6, '业务上线更新变更'),
    )
    asset = models.ForeignKey('Asset', blank=True, null=True, on_delete=models.SET_NULL)  # 当资产审批成功时有这项数据
    new_asset = models.ForeignKey('NewAssetApprovalZone', blank=True, null=True,
                                  on_delete=models.SET_NULL)  # 当资产审批失败时有这项数据
    event_type = models.SmallIntegerField('事件类型', choices=event_type_choice, default=4)
    component = models.CharField('事件子项', max_length=256, blank=True, null=True)
    detail = models.TextField('事件详情')
    date = models.DateTimeField('事件时间', auto_now_add=True)
    user = models.ForeignKey(User, blank=True, null=True, verbose_name='事件执行人',
                             on_delete=models.SET_NULL)  # 自动更新资产数据时没有执行人
    memo = models.TextField('备注', blank=True, null=True)

    def __str__(self):
        return self.name

    class Meta:
        verbose_name = '事件纪录'
        verbose_name_plural = "事件纪录"


class NewAssetApprovalZone(models.Model):
    """新资产待审批区"""

    sn = models.CharField('资产SN号', max_length=128, unique=True)  # 此字段必填
    asset_type_choice = (
        ('server', '服务器'),
        ('networkdevice', '网络设备'),
        ('storagedevice', '存储设备'),
        ('securitydevice', '安全设备'),
        ('IDC', '机房'),
        ('software', '软件资产'),
    )
    asset_type = models.CharField(choices=asset_type_choice, default='server', max_length=64, blank=True, null=True,
                                  verbose_name='资产类型')

    manufacturer = models.CharField(max_length=64, blank=True, null=True, verbose_name='生产厂商')
    model = models.CharField(max_length=128, blank=True, null=True, verbose_name='型号')
    ram_size = models.PositiveIntegerField(blank=True, null=True, verbose_name='内存大小')
    cpu_model = models.CharField(max_length=128, blank=True, null=True, verbose_name='CPU型号')
    cpu_count = models.PositiveSmallIntegerField(blank=True, null=True)
    cpu_core_count = models.PositiveSmallIntegerField(blank=True, null=True)
    os_distribution = models.CharField(max_length=64, blank=True, null=True)
    os_type = models.CharField(max_length=64, blank=True, null=True)
    os_release = models.CharField(max_length=64, blank=True, null=True)

    data = models.TextField('资产数据')  # 此字段必填

    c_time = models.DateTimeField('汇报日期', auto_now_add=True)
    m_time = models.DateTimeField('数据更新日期', auto_now=True)
    approved = models.BooleanField('是否批准', default=False)

    def __str__(self):
        return self.sn

    class Meta:
        verbose_name = '新上线待批准资产'
        verbose_name_plural = "新上线待批准资产"
        ordering = ['-c_time']

报错信息如下：

Django报错处理：

SystemCheckError: System check identified some issues:

ERRORS:
assets.Asset.admin: (fields.E300) Field defines a relation with model 'User', which is either not installed, or is abstract.
assets.Asset.admin: (fields.E307) The field assets.Asset.admin was declared with a lazy reference to 'assets.user', but app 'assets' doesn't provide model 'user'.
assets.Asset.approved_by: (fields.E300) Field defines a relation with model 'User', which is either not installed, or is abstract.
assets.Asset.approved_by: (fields.E307) The field assets.Asset.approved_by was declared with a lazy reference to 'assets.user', but app 'assets' doesn't provide model 'user'.
assets.EventLog.user: (fields.E300) Field defines a relation with model 'User', which is either not installed, or is abstract.
assets.EventLog.user: (fields.E307) The field assets.EventLog.user was declared with a lazy reference to 'assets.user', but app 'assets' doesn't provide model 'user'.

 解决方案：

1、在settings.py中添加如下配置：

SILENCED_SYSTEM_CHECKS = ['fields.E300', 'fields.E307']

2、将models.py文件中的'User'去掉双引号，改为User，具体见下图所示：

3、再次执行数据库迁移操作：

python manage.py makemigrations
python manage.py migrate

4、数据库表完成创建，日志如下：