Drop use of deprecated imghdr standard library module

which has been removed in the upcoming Python 3.13 .

lib/galaxy/util/image_util.py

@@ -1,6 +1,5 @@
 """Provides utilities for working with image files."""
 
-import imghdr
 import logging
 from typing import (
     List,
@@ -22,11 +21,7 @@ def image_type(filename: str) -> Optional[str]:
             with Image.open(filename) as im:
                 fmt = im.format
         except Exception:
-            # We continue to try with imghdr, so this is a rare case of an
-            # exception we expect to happen frequently, so we're not logging
             pass
-    if not fmt:
-        fmt = imghdr.what(filename)
     if fmt:
         return fmt.upper()
     else:

test/unit/util/test_checkers.py

@@ -1,6 +1,10 @@
+import os.path
 import tempfile
 
-from galaxy.util.checkers import check_html
+from galaxy.util.checkers import (
+    check_html,
+    check_image,
+)
 
 
 def test_check_html():
@@ -17,3 +21,10 @@ def test_check_html():
         tmpb.write(b"\x1f\x8b")
         tmpb.flush()
         assert not check_html(tmpb.name)
+
+
+def test_check_image():
+    for filename, expected in (("1.tiff", True), ("454Score.png", True), ("1.bam", False)):
+        path = f"test-data/{filename}"
+        assert os.path.exists(path)
+        assert check_image(path) is expected