Fix error when no backup URL provided

docs/release_notes/index.md

@@ -9,6 +9,7 @@ is available in the [commit logs](https://github.com/YosefLab/scvi-tools/commits
 ```{toctree}
 :maxdepth: 2
 
+v0.16.2
 v0.16.1
 v0.16.0
 ```

docs/release_notes/v0.16.2.md

@@ -0,0 +1,19 @@
+# New in 0.16.2 (2022-MM-DD)
+
+## Changes
+
+## Breaking changes
+
+## Bug Fixes
+- Raise appropriate error when `backup_url` is not provided and file is missing on {meth}`~scvi.model.base.BaseModelClass.load` ([#1527]).
+
+## Contributors
+
+- [@jjhong922]
+- [@adamgayoso]
+
+[#1527]: https://github.com/YosefLab/scvi-tools/pull/1527
+
+
+[@adamgayoso]: https://github.com/adamgayoso
+[@jjhong922]: https://github.com/jjhong922

scvi/data/_download.py

@@ -1,6 +1,7 @@
 import logging
 import os
 import urllib
+from typing import Optional
 
 import numpy as np
 
@@ -9,10 +10,15 @@
 logger = logging.getLogger(__name__)
 
 
-def _download(url: str, save_path: str, filename: str):
+def _download(url: Optional[str], save_path: str, filename: str):
     """Writes data from url to file."""
     if os.path.exists(os.path.join(save_path, filename)):
-        logger.info("File %s already downloaded" % (os.path.join(save_path, filename)))
+        logger.info(f"File {os.path.join(save_path, filename)} already downloaded")
+        return
+    elif url is None:
+        logger.info(
+            f"No backup URL provided for missing file {os.path.join(save_path, filename)}"
+        )
         return
     req = urllib.request.Request(url, headers={"User-Agent": "Magic Browser"})
     try: