Sanitize report file extension

issue3446
(transplanted from 357d0a4d9cb8b3f0f4192cb87996a5720bf1cb37)

--HG--
extra : transplant_source : 5%7D%0AM%9C%B8%B3%F0%F4%19%2C%B8y%96%A5r%0B%F1%CB7
Prepare release 2.8.4
Added tag 2.8.4 for changeset 78235f4de38c
Increase version number