handle check task being cancelled while view is shown

subiquity/controllers/refresh.py

@@ -65,9 +65,7 @@ class RefreshController(BaseController):
     @property
     def check_state(self):
         task = self.check_task.task
-        if not task.done():
-            return CheckState.UNKNOWN
-        if task.cancelled():
+        if not task.done() or task.cancelled():
             return CheckState.UNKNOWN
         if task.exception():
             return CheckState.UNAVAILABLE

subiquity/ui/views/refresh.py

@@ -163,10 +163,18 @@ class RefreshView(BaseView):
         schedule_task(self._wait_check_result())
 
     async def _wait_check_result(self):
+        while True:
             try:
                 check_state = await self.controller.check_task.task
+            except asyncio.CancelledError:
+                # If the task was cancelled, another will have been
+                # started.
+                continue
             except Exception as e:
                 self.check_state_failed(e)
+                return
+            else:
+                break
         if check_state == CheckState.AVAILABLE:
             self.check_state_available()
         else: