For some reason Angular would send all requests over HTTP if you don’t have a tailing / at the end of your requests. Even if the page itself is served through HTTPS.
$http.get('/someUrl').success(successCallback); // Request would go over HTTP even if the page is served via HTTPS
But if you add a leading / everything would work as expected:
$http.get('/someUrl/').success(successCallback); // This would be sent over HTTPS if the page is served via HTTPS
EDIT: The root cause of this problem is that Angular looks at the actual headers from the server. If you have an incorrect internal pass of http data through https there will still be http headers and Angular would use them if you do not add / at the end.
i.e. If you have an NGINX serving content through https, but passing requests to Gunicorn on the backend via http, you might have this issue. The way to fix that is to pass the correct headers to Gunicorn, so your framework would be under the impression of being served via https. In NGINX you can do this with the following line:
proxy_set_header X-Forwarded-Proto $scheme;