installation fails with python >= 3.9

[wkotlarski]

Installation with python 3.10 fails with the following error

mprpc/client.c: In function ‘__Pyx_modinit_type_init_code’:
mprpc/client.c:6372:38: error: ‘PyTypeObject’ {aka ‘struct _typeobject’} has no member named ‘tp_print’
6372 |   __pyx_type_5mprpc_6client_RPCClient.tp_print = 0;

I believe that in python 3.9 this slot was renamed to tp_vectorcall_offset (see here)