replace deprecated stdlib imghdr with filetype

Author: jans-code

bash_kernel/display.py

@@ -52,11 +52,12 @@
 is your friend to debug the format of the content message.
 """
 import base64
-import imghdr
 import json
 import os
 import re
 
+import filetype
+
 
 _TEXT_SAVED_IMAGE = "bash_kernel: saved image data to: "
 _TEXT_SAVED_HTML = "bash_kernel: saved html data to: "
@@ -101,8 +102,7 @@ def display_data_for_image(filename):
     with open(filename, 'rb') as f:
         image = f.read()
     _unlink_if_temporary(filename)
-
-    image_type = imghdr.what(None, image)
+    image_type = filetype.image_match(image).extension
     if image_type is None:
         raise ValueError("Not a valid image: %s" % image)
 

pyproject.toml

@@ -8,7 +8,7 @@ authors = [
     {name = "Thomas Kluyver", email = "thomas@kluyver.me.uk"},
 ]
 readme = "README.rst"
-dependencies = ["pexpect (>=4.0)", "ipykernel"]
+dependencies = ["pexpect (>=4.0)", "ipykernel", "filetype"]
 classifiers = [
     "Framework :: Jupyter",
     "License :: OSI Approved :: BSD License",