Decode bytes before passing to f-string

Tests/test_file_ppm.py

@@ -123,7 +123,7 @@ def test_token_too_long(tmp_path):
         with Image.open(path):
             pass
 
-    assert str(e.value) == "Token too long in file header: b'01234567890'"
+    assert str(e.value) == "Token too long in file header: 01234567890"
 
 
 def test_truncated_file(tmp_path):

src/PIL/PpmImagePlugin.py

@@ -83,7 +83,7 @@ class PpmImageFile(ImageFile.ImageFile):
             # Token was not even 1 byte
             raise ValueError("Reached EOF while reading header")
         elif len(token) > 10:
-            raise ValueError(f"Token too long in file header: {token}")
+            raise ValueError(f"Token too long in file header: {token.decode()}")
         return token
 
     def _open(self):