def _make_header_wsgi_env_key(http_header: str) ->str:
    """Convert HTTP header to WSGI environ key format.

    HTTP_ Variables corresponding to the client-supplied HTTP request
    headers (i.e., variables whose names begin with "HTTP_").
    See https://www.python.org/dev/peps/pep-3333/ for more details

    >>> print(_make_header_wsgi_env_key("X-USERNAME"))
    HTTP_X_USERNAME
    """
    return 'HTTP_' + http_header.replace('-', '_').upper()
