Better fix for #2 (Crashes when encountering files that aren't images)

* Only ignore invalid files in the `autotag` script, not in the
  web service. In the web service we want to return an error if given an
  invalid or corrupt file.

* Use the logger to log a warning instead of printing directly to stderr.

autotag

@@ -3,6 +3,8 @@
 import json
 import click
 import itertools
+import logging
+import PIL
 from autotagger import Autotagger
 from pathlib import Path
 from more_itertools import ichunked
@@ -29,12 +31,11 @@ def main(files, threshold, limit, bs, csv, input_file, group_tags, name_only, mo
         click.get_current_context().exit()
 
     for filepaths in ichunked(paths, bs):
-        filepaths = list(filepaths)
-        files = [click.open_file(filepath, "rb") for filepath in filepaths]
+        files = list(filter(None, [open_image(filepath) for filepath in filepaths]))
         predictions = autotagger.predict(files, threshold=threshold, limit=limit, bs=bs)
 
-        for filepath, tags in zip(filepaths, predictions):
-            output_result(filepath, tags, csv, group_tags, name_only)
+        for file, tags in zip(files, predictions):
+            output_result(Path(file.name), tags, csv, group_tags, name_only)
 
 def output_result(filepath, tags, csv, group_tags, name_only):
     name = filepath.stem if name_only else str(filepath)
@@ -60,5 +61,20 @@ def get_filepaths(paths):
 def recurse_dir(directory):
     return (path for path in directory.glob("**/*") if not path.is_dir())
 
+def open_image(filepath):
+    try:
+        # Load the image to check that it's a valid file. Open the file twice because PIL closes the underlying file.
+        file = click.open_file(filepath, "rb")
+        image = PIL.Image.open(file)
+        image.load()
+        image.close()
+        return click.open_file(filepath, "rb")
+    except PIL.UnidentifiedImageError as err:
+        logging.warning(f"Skipped {filepath} (not an image)")
+        return None
+    except Exception as err:
+        logging.warning(f"Skipped {filepath} ({type(err).__name__}: {str(err)})")
+        return None
+
 if __name__ == "__main__":
     main()