The open redirect protection for this example is still vulnerable

A target like https:/example.com (notice the single /) will be parsed as having no netloc, but browsers will redirect to https://example.com (tested on Firefox and Chrome using Fedora).

from urllib.parse import urlparse

print(urlparse('https:/example.com'))
# ParseResult(scheme='https', netloc='', path='/example.com', params='', query='', fragment='')

See Django for example

https://github.com/django/django/blob/f339c4c8e4870f23d3ba8bf8ee68c57628739592/django/utils/http.py#L356-L361