disable cache for logos objects

app/views/scodoc.py

@@ -30,6 +30,7 @@ Module main: page d'accueil, avec liste des départements
 
 Emmanuel Viennet, 2021
 """
+import datetime
 import io
 
 import wtforms.validators
@@ -231,7 +232,11 @@ def _return_logo(name="header", dept_id="", small=False, strict: bool = True):
                 stream.seek(0)
                 return send_file(stream, mimetype=f"image/{fmt}")
         else:
-            return send_file(logo.filepath, mimetype=f"image/{suffix}")
+            return send_file(
+                logo.filepath,
+                mimetype=f"image/{suffix}",
+                last_modified=datetime.datetime.now(),
+            )
     else:
         abort(404)