HTTP headers are presented in WSGI environment with 'HTTP_' prefix.
        This method finds those headers, removes the prefix, converts
        underscores to dashes, and converts to lower case.

        :param wsgi_environ:
        :return: returns a dictionary of headers

def _parse_wsgi_headers(wsgi_environ):
        """
        HTTP headers are presented in WSGI environment with 'HTTP_' prefix.
        This method finds those headers, removes the prefix, converts
        underscores to dashes, and converts to lower case.

        :param wsgi_environ:
        :return: returns a dictionary of headers
        """
        prefix = 'HTTP_'
        p_len = len(prefix)
        # use .items() despite suspected memory pressure bc GC occasionally
        # collects wsgi_environ.iteritems() during iteration.
        headers = {
            key[p_len:].replace('_', '-').lower():
                val for (key, val) in wsgi_environ.items()
            if key.startswith(prefix)}
        return headers