mgr: set argv for python in PyModuleRegistry

before this change, we setup the progname for Python interpreter,
but setup the argv for it in PyModule. and we are using deprecated
API to initialize Python interpreter.

in this change, let's do this in a single place for better
maintainability. also, take this opportunity, to use the non-deprecated
API to initialize interpreter on Python >= 3.8.

this silence the warning when compiling ceph-mgr with CPython 3.12:
```
/var/ssd/ceph/src/mgr/PyModule.cc: In member function ‘int PyModule::load(PyThreadState*)’:
/var/ssd/ceph/src/mgr/PyModule.cc:363:20: warning: ‘void PySys_SetArgv(int, wchar_t**)’ is deprecated [-Wdeprecated-declarations]
  363 |       PySys_SetArgv(1, (wchar_t**)argv);
      |       ~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~
In file included from /usr/include/python3.12/Python.h:96,
                 from /var/ssd/ceph/src/mgr/BaseMgrModule.h:4,
                 from /var/ssd/ceph/src/mgr/PyModule.cc:14:
/usr/include/python3.12/sysmodule.h:13:38: note: declared here
   13 | Py_DEPRECATED(3.11) PyAPI_FUNC(void) PySys_SetArgv(int, wchar_t **);
      |                                      ^~~~~~~~~~~~~
```

Signed-off-by: Kefu Chai <[email protected]>

Author: tchaikov

src/mgr/PyModule.cc

@@ -357,10 +357,6 @@ int PyModule::load(PyThreadState *pMainThreadState)
       return -EINVAL;
     } else {
       pMyThreadState.set(thread_state);
-      // Some python modules do not cope with an unpopulated argv, so lets
-      // fake one.  This step also picks up site-packages into sys.path.
-      const wchar_t *argv[] = {L"ceph-mgr"};
-      PySys_SetArgv(1, (wchar_t**)argv);
       // Configure sys.path to include mgr_module_path
       string paths = (g_conf().get_val<std::string>("mgr_module_path") + ':' +
                       get_site_packages() + ':');

src/mgr/PyModuleRegistry.cc

@@ -70,6 +70,11 @@ void PyModuleRegistry::init()
   PyStatus status;
   status = PyConfig_SetString(&py_config, &py_config.program_name, WCHAR(MGR_PYTHON_EXECUTABLE));
   ceph_assertf(!PyStatus_Exception(status), "PyConfig_SetString: %s:%s", status.func, status.err_msg);
+  // Some python modules do not cope with an unpopulated argv, so lets
+  // fake one.  This step also picks up site-packages into sys.path.
+  const wchar_t* argv[] = {L"ceph-mgr"};
+  status = PyConfig_SetArgv(&py_config, 1, (wchar_t *const *)argv);
+  ceph_assertf(!PyStatus_Exception(status), "PyConfig_SetArgv: %s:%s", status.func, status.err_msg);
   // Add more modules
   if (g_conf().get_val<bool>("daemonize")) {
     PyImport_AppendInittab("ceph_logger", PyModule::init_ceph_logger);
@@ -85,6 +90,8 @@ void PyModuleRegistry::init()
   }
   PyImport_AppendInittab("ceph_module", PyModule::init_ceph_module);
   Py_InitializeEx(0);
+  const wchar_t *argv[] = {L"ceph-mgr"};
+  PySys_SetArgv(1, (wchar_t**)argv);
 #endif // PY_VERSION_HEX >= 0x03080000
 #undef WCHAR