Read SAB cat as category

Treat SAB history cat/category fields equivalently for #20.

tests/test_sab_readiness.py

@@ -22,6 +22,11 @@ def test_wrong_category_ignored():
     assert result.state == "ignored"
 
 
+def test_sab_cat_field_is_treated_as_category():
+    result = classify_history_item(item(category=None, cat="manual"), set(), "manual", ROOT)
+    assert result.ready
+
+
 def test_queue_item_not_ready():
     result = classify_history_item(item(), {"1"}, "manual", ROOT)
     assert result.state == "processing"