Show if lesson is cancelled. Closes #31.

biscuit/apps/chronos/tables.py

@@ -10,8 +10,10 @@ from .models import LessonPeriod
 
 
 def _css_class_from_lesson_state(record: Optional[LessonPeriod] = None, table: Optional[LessonsTable] = None) -> str:
-    if record.get_substitution(record._week):
-        return 'table-warning'
+    if record.get_substitution(record._week).cancelled:
+        return 'table-danger'
+    elif record.get_substitution(record._week):
+        return 'table-warnig'
     else:
         return ''