fix(worker): catch mutagen TypeError when saving metadata (#3182)

Mutagen may fail with:

```
worker-1  | Traceback (most recent call last):
worker-1  |   File "/usr/local/lib/python3.10/site-packages/celery/app/trace.py", line 412, in trace_task
worker-1  |     R = retval = fun(*args, **kwargs)
worker-1  |   File "/usr/local/lib/python3.10/site-packages/celery/app/trace.py", line 704, in __protected_call__
worker-1  |     return self.run(*args, **kwargs)
worker-1  |   File "/src/libretime_worker/tasks.py", line 114, in podcast_download
worker-1  |     metadata["artist"] = podcast_name
worker-1  |   File "/usr/local/lib/python3.10/site-packages/mutagen/_file.py", line 74, in __setitem__
worker-1  |     self.tags[key] = value
worker-1  |   File "/usr/local/lib/python3.10/site-packages/mutagen/id3/_tags.py", line 341, in __setitem__
worker-1  |     raise TypeError("%r not a Frame instance" % tag)
worker-1  | TypeError: "Infos du soir" not a Frame instance
```

This TypeError was raised when I trying to write metadata to a wave
file.

This patch ensures that the error is reported back to the frontend. It
also improve the error messages being reported.

worker/libretime_worker/tasks.py

@@ -60,6 +60,12 @@ def legacy_trigger_task_manager():
     legacy_client.trigger_task_manager()
 
 
+class PodcastDownloadException(Exception):
+    """
+    An error occurred during the podcast download task.
+    """
+
+
 @worker.task(name="podcast-download", acks_late=True)
 def podcast_download(
     episode_id: int,
@@ -98,15 +104,16 @@ def podcast_download(
                         tmp_file.write(chunk)
 
         except RequestException as exception:
-            logger.exception("could not download podcast episode %s", episode_id)
-            raise exception
+            raise PodcastDownloadException(
+                f"could not download podcast episode {episode_id}: {exception}"
+            ) from exception
 
         # Save metadata to podcast episode file
         try:
             metadata = mutagen.File(tmp_file.name, easy=True)
             if metadata is None:
-                raise MutagenError(
-                    f"could not determine episode {episode_id} file type"
+                raise PodcastDownloadException(
+                    f"could not determine podcast episode {episode_id} file type"
                 )
 
             if override_album:
@@ -122,9 +129,10 @@ def podcast_download(
             metadata.save()
             logger.debug("saved metadata %s", metadata)
 
-        except MutagenError as exception:
-            logger.exception("could not save episode %s metadata", episode_id)
-            raise exception
+        except (MutagenError, TypeError) as exception:
+            raise PodcastDownloadException(
+                f"could not save podcast episode {episode_id} metadata: {exception}"
+            ) from exception
 
         # Upload podcast episode file
         try:
@@ -141,10 +149,12 @@ def podcast_download(
                 result["status"] = 1
 
         except RequestException as exception:
-            logger.exception("could not upload episode %s", episode_id)
-            raise exception
+            raise PodcastDownloadException(
+                f"could not upload podcast episode {episode_id}: {exception}"
+            ) from exception
 
-    except (RequestException, MutagenError) as exception:
+    except PodcastDownloadException as exception:
+        logger.exception(exception)
         result["status"] = 0
         result["error"] = str(exception)
 

worker/tests/tasks_test.py

@@ -53,7 +53,7 @@ def test_podcast_download_invalid_file(requests_mock):
     assert json.loads(result) == {
         "episodeid": 1,
         "status": 0,
-        "error": "could not determine episode 1 file type",
+        "error": "could not determine podcast episode 1 file type",
     }