added warnings when asset files cannot be loaded

rio/app_server/fastapi_server.py

@@ -9,6 +9,7 @@ import json
 import logging
 import secrets
 import typing as t
+import warnings
 import weakref
 from datetime import timedelta
 from pathlib import Path
@@ -622,6 +623,17 @@ Sitemap: {base_url / "/rio/sitemap"}
                     image.save(output_buffer, format="png")
 
             except Exception as err:
+                if isinstance(self.app._icon, assets.PathAsset):
+                    warnings.warn(
+                        f"Could not fetch the app's icon from {self.app._icon.path.resolve()}"
+                    )
+                elif isinstance(self.app._icon, assets.UrlAsset):
+                    warnings.warn(
+                        f"Could not fetch the app's icon from {self.app._icon.url}"
+                    )
+                else:
+                    warnings.warn(f"Could not fetch the app's icon from")
+
                 raise fastapi.HTTPException(
                     status_code=fastapi.status.HTTP_500_INTERNAL_SERVER_ERROR,
                     detail="Could not fetch the app's icon.",

rio/byte_serving.py

@@ -7,6 +7,7 @@ https://github.com/tiangolo/fastapi/issues/1240#issuecomment-1055396884
 
 import mimetypes
 import typing as t
+import warnings
 from pathlib import Path
 
 import fastapi
@@ -71,13 +72,15 @@ def range_requests_response(
     Returns a fastapi response which serves the given file, supporting Range
     Requests as per RFC7233 ("HTTP byte serving").
 
-    Returns a 404 if the file does not exist.
+    Returns a 404 if the file does not exist. In this case a warning is also
+    shown in the console.
     """
 
     # Get the file size. This also verifies the file exists.
     try:
         file_size_in_bytes = file_path.stat().st_size
     except FileNotFoundError:
+        warnings.warn(f"Cannot find file at {file_path.resolve()}")
         return fastapi.responses.Response(status_code=404)
 
     # Prepare response headers