Build fails if using external storage (such as S3)

[glitchwolfe]

I am using Amazon S3 (via boto3) to store the media files for a wagtail/django project. When I try to build my site, I get a ResourceNotFound error showing that it's looking for my S3 bucket inside my local directory, rather than remotely:

fs.errors.ResourceNotFound: resource '/Users/me/Documents/Django-Project/bakery/https:/s3-region-name-here.amazonaws.com/django-project-media/media' not found

The build command does work if I copy all of my media to my local directory, but it would definitely be ideal if I did not have to do that, especially since I intend to automate the build process. I acknowledge my use case is pretty unusual, so I understand if this is more of an enhancement request than a bug.

Error log attached below (some info changed for privacy reasons).

---

Full Error Log

(app) xxxxxxxxxx:Django-Project $ ./manage.py build
Traceback (most recent call last):
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/fs/osfs.py", line 324, in makedir
    os.mkdir(sys_path, mode)
FileNotFoundError: [Errno 2] No such file or directory: b'/Users/me/Documents/Django-Project/bakery/https:/s3-region-name-here.amazonaws.com/django-project-media/media'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "./manage.py", line 12, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/django/core/management/__init__.py", line 371, in execute_from_command_line
    utility.execute()
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/django/core/management/__init__.py", line 365, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/django/core/management/base.py", line 288, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/django/core/management/base.py", line 335, in execute
    output = self.handle(*args, **options)
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/bakery/management/commands/build.py", line 109, in handle
    self.build_media()
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/bakery/management/commands/build.py", line 223, in build_media
    copy.copy_dir("osfs:///", smart_text(self.media_root), self.fs, smart_text(target_dir))
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/fs/copy.py", line 293, in copy_dir
    _dst_fs.makedir(_dst_path, recreate=True)
  File "/Users/me/.virtualenvs/Django-Project/lib/python3.6/site-packages/fs/osfs.py", line 327, in makedir
    raise errors.ResourceNotFound(path)
fs.errors.ResourceNotFound: resource '/Users/me/Documents/Django-Project/bakery/https:/s3-region-name-here.amazonaws.com/django-project-media/media' not found

Relevant Settings

# ----- settings.py -----

# Media Storage
MEDIAFILES_LOCATION = 'media'
MEDIA_URL = "https://s3-{}.amazonaws.com/{}/{}/".format(AWS_S3_REGION_NAME, AWS_STORAGE_BUCKET_NAME, MEDIAFILES_LOCATION)
DEFAULT_FILE_STORAGE = 'custom_storages.MediaStorage'

# Wagtail Bakery Settings
BUILD_DIR = os.path.join(BASE_DIR, 'bakery')
BAKERY_MULTISITE = True
BAKERY_VIEWS = (
    'wagtailbakery.views.AllPublishedPagesView',
)

# ----- custom_storages.py -----
from django.conf import settings
from storages.backends.s3boto3 import S3Boto3Storage

class MediaStorage(S3Boto3Storage):
    location = settings.MEDIAFILES_LOCATION