When opening a .dxf file saved by QCAD with a name containing a special characters (tested with diacritics), it fails with the following message:

Cannot open file
'E:/tèst1.dxf'
Import failed.

How to reproduce:
1 - Save a file (content doesn't matter, it's the same with an empty file and a file containing data) using the name "tèst1.dxf"
2 - Try to open the file
3 - Error message

What is expected:
The file open.

Note that the problem doesn't lie in the "save" step: the same file, once renamed to "test1.dxf" opens fine.