Handle non-existing users in register_cas_account

authens/shortcuts.py

@@ -59,7 +59,11 @@ def register_cas_account(user: User, cas_login: str) -> CASAccount:
     if OldCASAccount.objects.filter(user=user).exists():
         raise ValueError("User '{}' has an old CAS account".format(user))
 
-    entrance_year = fetch_cas_account(cas_login)["entrance_year"]
+    ldap_info = fetch_cas_account(cas_login)
+    if ldap_info is None:
+        raise ValueError("There is no LDAP user for id '{}'".format(cas_login))
+
+    entrance_year = ldap_info["entrance_year"]
     return CASAccount.objects.create(
         user=user, cas_login=cas_login, entrance_year=entrance_year
     )