unit tests failing in newer python versions (3.8) because self.thumbnails cannot be appended to

[MoralCode]

python version 3.8.6 (using pyenv, although it may inadvertently have been using 3.10)
dependencies installed: the ones in requirements-dev.txt in addition to sqlalchemy python-magic pillow flask_cors via pipenv

Procedure: use command python -m pipenv run python3 -m unittest or similar to run the unit tests while in the sqlalchemy-media directory.

Expected: tests pass

Actual: tests are failing

Output (the last part of it at least):

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ERROR: sqlalchemy_media.tests.test_google_cloud_storge (unittest.loader._FailedTest)
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ImportError: Failed to import test module: sqlalchemy_media.tests.test_google_cloud_storge
Traceback (most recent call last):
  File "/usr/lib/python3.10/unittest/loader.py", line 436, in _find_test_path
    module = self._get_module_from_name(name)
  File "/usr/lib/python3.10/unittest/loader.py", line 377, in _get_module_from_name
    __import__(name)
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/tests/test_google_cloud_storge.py", line 7, in <module>
    from sqlalchemy_media.stores.GoogleCloudStorage import GoogleCloudStorge
ImportError: cannot import name 'GoogleCloudStorge' from 'sqlalchemy_media.stores.GoogleCloudStorage' (/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/stores/GoogleCloudStorage.py)


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ERROR: test_image_list (sqlalchemy_media.tests.test_image.ImageTestCase)
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Traceback (most recent call last):
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/tests/test_image.py", line 291, in test_image_list
    thumbnail = person1.images[0].get_thumbnail(
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 862, in get_thumbnail
    return self.generate_thumbnail(width, height, ratio)
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 816, in generate_thumbnail
    self.thumbnails.append((width, height, ratio, thumbnail))
AttributeError: 'NoneType' object has no attribute 'append'

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ERROR: test_image_thumbnail_pre_generate (sqlalchemy_media.tests.test_image.ImageTestCase)
Issue #72
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Traceback (most recent call last):
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/tests/test_image.py", line 237, in test_image_thumbnail_pre_generate
    person1.image.generate_thumbnail(width=100)
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 816, in generate_thumbnail
    self.thumbnails.append((width, height, ratio, thumbnail))
AttributeError: 'NoneType' object has no attribute 'append'

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ERROR: test_thumbnail (sqlalchemy_media.tests.test_image.ImageTestCase)
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Traceback (most recent call last):
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/tests/test_image.py", line 64, in test_thumbnail
    thumbnail = person1.image.get_thumbnail(
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 862, in get_thumbnail
    return self.generate_thumbnail(width, height, ratio)
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 816, in generate_thumbnail
    self.thumbnails.append((width, height, ratio, thumbnail))
AttributeError: 'NoneType' object has no attribute 'append'

======================================================================
ERROR: test_thumbnail_delete (sqlalchemy_media.tests.test_image.ImageTestCase)
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Traceback (most recent call last):
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/tests/test_image.py", line 182, in test_thumbnail_delete
    thumbnail = person1.image.get_thumbnail(
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 862, in get_thumbnail
    return self.generate_thumbnail(width, height, ratio)
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 816, in generate_thumbnail
    self.thumbnails.append((width, height, ratio, thumbnail))
AttributeError: 'NoneType' object has no attribute 'append'

======================================================================
ERROR: test_rrs_put (sqlalchemy_media.tests.test_s3_store.S3StoreTestCase)
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Traceback (most recent call last):
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/tests/test_s3_store.py", line 93, in test_rrs_put
    thumbnail = person1.image.get_thumbnail(
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 862, in get_thumbnail
    return self.generate_thumbnail(width, height, ratio)
  File "/home/ace/Projects/Current/GenericInventory/sqlalchemy-media/contrib/sqlalchemy-media/sqlalchemy_media/attachments.py", line 816, in generate_thumbnail
    self.thumbnails.append((width, height, ratio, thumbnail))
AttributeError: 'NoneType' object has no attribute 'append'

----------------------------------------------------------------------
Ran 83 tests in 10.306s

FAILED (errors=6)

the error seems to be due to a lack of ability to set self.thumbnails in attachments.py line 815. it seems like this might be due to changes made to python in newer versions (and thus related somewhat to #131)

[MoralCode]

I believe I have solved the problem on my fork of this repo