@require_login(): made all arguments keyword-only

This allows us to remove the require_roles kwarg at some point, ensuring
that it doesn't fall back to assigning to require_cap instead when that
happens. It's also more explicit everywhere, so it's clearer when we check
for roles or caps.

pillar/api/utils/authorization.py

@@ -276,7 +276,7 @@ def merge_permissions(*args):
     return effective
 
 
-def require_login(require_roles=set(),
+def require_login(*, require_roles=set(),
                   require_cap='',
                   require_all=False,
                   redirect_to_login=False):