If one goes here:
HTTP 1 headers encoding is a legacy subject (latin-1 etc), as mentioned here:
My hypothesis is the crash is completely accent-related (and linked to latin-1 <-> UTF-8 transcoding probably).
If one inputs "ephemere", the crash stops.
While a bit exotic, this point is essential for the content-disposition header, which gives the filename of the downloaded file (attachment, filename=xyz).