Problème pour générer des miniatures

from django.db import models
from django.core.files.base import ContentFile

class Picture(models.Model):

    IMAGE_SIZES = {
        'thumbnail' : (360, 225)
    }

    title = models.CharField(max_length=64, verbose_name='titre')
    description = models.TextField(null=True, verbose_name='description')
    date = models.DateTimeField(auto_now_add=True, auto_now=False, verbose_name="date d'upload")
    picture = models.ImageField(upload_to='images/', verbose_name='image')

    class Meta:
        verbose_name = "Image"
        verbose_name_plural = "Images"

    def __str__(self):
        return self.title

    def save(self):
        from PIL import Image
        #Original photo
        imgFile = Image.open(self.picture.path)

        #Convert to RGB
        if imgFile.mode not in ('L', 'RGB'):
            imgFile = imgFile.convert('RGB')

        #Save a thumbnail for each of the given dimensions
        #The IMAGE_SIZES looks like:
        #IMAGE_SIZES = { 'image_web'      : (300, 348),
        #                'image_large'    : (600, 450),
        #                'image_thumb'    : (200, 200) }
        #each of which corresponds to an ImageField of the same name
        for field_name, size in self.IMAGE_SIZES.iteritems():
            field = getattr(self, field_name)
            working = imgFile.copy()
            working.thumbnail(size, Image.ANTIALIAS)
            fp = StringIO()
            working.save(fp, "JPEG", quality=95)
            cf = ContentFile(fp.getvalue())
            field.save(name=self.picture.name, content=cf, save=False);

        #Save instance of Photo
        super(Photo, self).save()

FileNotFoundError: [Errno 2] No such file or directory: '/home/louis/Documents/blog/lens/media/plane.png'