exactly like the function in WSGI 1.0, but it is required to emit a
deprecation warning to warns about this function being obsolete.
`write()` will be remove in WSGI 2.0, which will be based on WSGI 1.1.
+The same rule applies for the `exc_info`. If this parameter is used in
+WSGI 1.1, the server must still handle it, but warn with a deprecation