I use the wsgi_handler instead of roundup-server. And I can not get
HTTP_X-REQUESTED-WITH set in environment because WSGI server convert all
'-' into '_'. So the X-Requested-With header becomes
HTTP_X_REQUESTED_WITH. But roundup-server use HTTP_X-REQUESTED-WITH key.
I think roundup-server behavior should be normalized with other WSGI
server and not use '-' in HTTP_*.
I could not find in PEP3333 that '-' should be converted into '_' for
HTTP_. There is only a reference to server-defined variables.

https://www.python.org/dev/peps/pep-3333/#environ-variables