Django throws 'UnicodeEncodeError' when using Cyrillic symbols to override field upload_to.

[Kirill]

So, I have a Book model, that contains some fields. But most important are:
'title' as 'CharField'
'pdf', 'epub', 'fb2' as 'FileField'
'image' as 'ImageField'
we will return to they in just a second...
My Book model also has overrided clean method. In that method I assign my title field value as upload_to value.

uploading_files = [
    self.image,
    self.pdf,
    self.fb2,
    self.epub
]
for file_ in uploading_files:
    file_.field.upload_to = self.title

Here is where bug hided. If I set title value to "Колобок", for example, it throws me an UnicodeEncodeError. This thing happends only when i first create model.
If I firstly will set title value as "Kolobok", and later rename it to "Колобок", I have no error.

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I already some kind of "fixed" this.
Endpoint of thrown exception was ...\django\db\models\fields\files.py. After fork from your Github, I followed this path, and find function that throws that error, that function was generate_filename in FileField class, line 305. After I added small correct...

try:
    dirname = datetime.datetime.now().strftime(self.upload_to)
except UnicodeEncodeError:
    dirname = self.upload_to

... all works fine now, and I can use Cyrillic symbols as my title and folder name in upload_to attribute.

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For comfort, here is my ​Github with all my Django code in it.