add "unknown" status (via allure-framework#523)

janza · web-flow · commit 901daab3765a · 2020-11-24T20:00:37.000+03:00
Allure report supports this status as well as the other ones.
diff --git a/allure-python-commons/src/model2.py b/allure-python-commons/src/model2.py
@@ -105,3 +105,4 @@ class Status(object):
     BROKEN = 'broken'
     PASSED = 'passed'
     SKIPPED = 'skipped'
+    UNKNOWN = 'unknown'
