Replace binaryornot library with a simple magic bytes check

The library has not been updated and does not have proper Python 3.13 support.
This same approach is used by Git internally to detect binary files.

Author: ihalaij1

exercise/submission_models.py

@@ -6,7 +6,6 @@
 from typing import IO, Dict, Iterable, List, Tuple, TYPE_CHECKING, Callable
 from urllib.parse import urlparse
 
-from binaryornot.check import is_binary
 from django.conf import settings
 from django.db import models, DatabaseError
 from django.db.models import F
@@ -865,9 +864,15 @@ def get_mime(self):
 
     def is_passed(self):
         if self.file_object.path.endswith(".pdf"):
-            # PDF files are sometimes incorrectly classified as non-binary by the 'binaryornot' library
             return True
-        return is_binary(self.file_object.path)
+        # Simple magic bytes check
+        path = self.file_object.path
+        try:
+            with open(path, 'rb') as f:
+                chunk = f.read(1024)
+            return b'\x00' in chunk
+        except OSError:
+            return False
 
 
     ABSOLUTE_URL_NAME = "submission-file"

requirements.txt

@@ -30,7 +30,6 @@ markdown ~= 3.3.4
 aplus-auth ~= 0.2.0
 celery >= 5.2.1, < 6
 redis >= 4
-binaryornot ~= 0.4.4
 django-model-utils ~= 4.2.0
 format_cef ~= 0.0.4
 PyLTI1p3 ~= 2.0.0