Compatibility with python-magic of latest version (returts str, not bytes)

boards/utils.py

@@ -137,8 +137,9 b' def get_upload_filename(model_instance, '
 
 
 def get_file_mimetype(file) -> str:
-    type = magic.from_buffer(file.chunks().__next__(), mime=True)
-    if type is not None:
-        return type.decode()
-    else:
-        return 'application/octet-stream'
+    file_type = magic.from_buffer(file.chunks().__next__(), mime=True)
+    if file_type is None:
+        file_type = 'application/octet-stream'
+    else if type(file_type) == bytes:
+        file_type = file_type.decode()
+    return type