Upgrade to Django 2.2 and modern DRF and py.test (#1246)

* Upgrade django and stuff

* Update to Django 2.2 and recent versions of similar packages

* Provide explicit orderings to all models used in paginated queries

* Resolve naive datetime warnings in test suite

* Deal with deprecation warnings

* Fix sqlparse version

src/pretix/base/views/js_catalog.py

@@ -2,7 +2,7 @@ from django.utils import timezone
 from django.utils.translation.trans_real import DjangoTranslation
 from django.views.decorators.cache import cache_page
 from django.views.decorators.http import etag
-from django.views.i18n import JavaScriptCatalog, render_javascript_catalog
+from django.views.i18n import JavaScriptCatalog
 
 # Yes, we want to regenerate this every time the module has been imported to
 # refresh the cache at least at every code deployment
@@ -21,4 +21,5 @@ js_info_dict = {
 def js_catalog(request, lang):
     c = JavaScriptCatalog()
     c.translation = DjangoTranslation(lang, domain='djangojs')
-    return render_javascript_catalog(c.get_catalog(), c.get_plural())
+    context = c.get_context_data()
+    return c.render_to_response(context)

src/pretix/base/views/metrics.py

@@ -20,10 +20,10 @@ def serve_metrics(request):
         return unauthed_response()
 
     # check if the user is properly authorized:
-    if "HTTP_AUTHORIZATION" not in request.META:
+    if "Authorization" not in request.headers:
         return unauthed_response()
 
-    method, credentials = request.META["HTTP_AUTHORIZATION"].split(" ", 1)
+    method, credentials = request.headers["Authorization"].split(" ", 1)
     if method.lower() != "basic":
         return unauthed_response()