TypeError：强制转换为Unicode：需要很长的字符串或缓冲区

class Movie(models.Model):
    movie_id = models.BigAutoField(primary_key=True)
    movie_name = models.CharField(max_length=128)
    movie_lang = models.CharField(max_length=36)
    director = models.CharField(max_length=72)
    producer = models.CharField(max_length=72)
    production_house = models.CharField(max_length=128)
    lead_actor = models.CharField(max_length=72)
    lead_actress = models.CharField(max_length=72)
    music_director = models.CharField(max_length=72)
    art_director = models.CharField(max_length=72)
    stunts = models.CharField(max_length=72)
    cinematography = models.CharField(max_length=72)
    costume_design = models.CharField(max_length=72)
    hair_stylist = models.CharField(max_length=72)  

    def __str__(self):
        return self.movie_name

class Cover(models.Model):
    cover_id = models.BigAutoField(primary_key=True)
    cover_path = models.CharField(max_length=512)
    movie = models.ForeignKey('Movie',on_delete=models.CASCADE) 

    def __str__(self):
        return self.cover_id

    def unicode(self):
        return unicode(self.cover_path)




#urls.py
from django.conf.urls import url

from . import views

urlpatterns = [
    url(r'^(?P<question_id>[0-9]+)/$',views.movie,name='movie'),
    url(r'^vedio/',views.vedio,name='vedio'),
    url(r'^image/',views.image,name='image'),
    url(r'^$',views.index,name = 'index'),
]

#views.py

from django.shortcuts import render

# Create your views here.
from django.http import HttpResponse

def index(request):
    return HttpResponse("Hello, world. You're at the movie station.")

def movie(request,question_id):
    return HttpResponse("Welcome to movies page")

def vedio(request):
    return HttpResponse("Welcome to vedios page")

def image(request):
    return HttpResponse("Welcome to images page")

环境：

请求方法：POST请求URL：http://localhost:8000/admin/movieaware/cover/add/

Django版本：1.10.3 Python版本：2.7.12已安装的应用程序：

['movieaware.apps.MovieawareConfig',
 'django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']

回溯：文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/core/handlers/exception.py”在内部39. response = get_response（request）文件“/ home / kartheek /Applications/anaconda2/lib/python2.7/site-packages/django/core/handlers/base.py“在_get_response 187. response = self.process_exception_by_middleware（e，request）File”/ home / kartheek / Applications / anaconda2 / lib / python2.7 / site-packages / django / core / handlers / base.py“在_get_response 185. response = wrapped_callback（request，* callback_args，** callback_kwargs）File”/ home / kartheek / Applications / anaconda2 / lib /包装544中的python2.7 / site-packages / django / contrib / admin / options.py“返回self.admin_site.admin_view（查看）（* args，** kwargs）文件”/ home / kartheek / Applications / anaconda2 / lib / python2.7 / site-packages / django / utils / decorators.py“in _wrapped_view 149. response = view_func（request，* args，** kwargs）File”/ home / kartheek / Applications / anaconda2 / lib / python2 . 7 / site-packages / django / views / decorators / cache.py“我n _wrapped_view_func 57. response = view_func（request，* args，** kwargs）内部文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/contrib/admin/sites.py” 211.返回视图（request，* args，** kwargs）add_view 1509中的文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/contrib/admin/options.py” self.changeform_view（request，None，form_url，extra_context）_wrapper 67中的文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/utils/decorators.py” . 返回bound_func（* args） ，** kwargs）文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/utils/decorators.py”在_wrapped_view 149. response = view_func（request，* args，** kwargs ）在bound_func 63中输入文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/utils/decorators.py” . 返回func.get（self，type（self））（* args2， ** kwargs2）文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/utils/decora tors.py“在内部185. return func（* args，** kwargs）文件”/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/contrib/admin/options.py“in changeform_view 1453. self_log_addition（request，new_object，change_message）log_addition 719中的文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/contrib/admin/options.py” . object_repr = force_text（object），文件“/home/kartheek/Applications/anaconda2/lib/python2.7/site-packages/django/utils/encoding.py”在force_text 78中.s = six.text_type（s）异常类型：TypeError at / admin / movieaware / cover / add / Exception值：强制转换为Unicode：需要很长的字符串或缓冲区

我已经尝试了大多数建议的解决方案，但没有任何工作 . 我无法弄清楚问题所在