Fix build on Python 3.10 (rhbz#1889726).

Backport two fixes:

* https://github.com/NLnetLabs/unbound/commit/e0d426ebb10653a78bf5c4053198f6ac19bfcd3e

* https://github.com/NLnetLabs/unbound/pull/427

diff --git a/libunbound/python/libunbound.i b/libunbound/python/libunbound.i

index a23c45b9c..ab244a6fb 100644

--- a/libunbound/python/libunbound.i

+++ b/libunbound/python/libunbound.i

@@ -916,7 +916,13 @@ int _ub_resolve_async(struct ub_ctx* ctx, char* name, int rrtype, int rrclass, v

       struct cb_data* id;

       id = (struct cb_data*) iddata;

       arglist = Py_BuildValue("(OiO)",id->data,status, SWIG_NewPointerObj(SWIG_as_voidptr(result), SWIGTYPE_p_ub_result, 0 |  0 ));   // Build argument list

+#if PY_MAJOR_VERSION <= 2 || (PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION < 9)

+      /* for python before 3.9 */

       fresult = PyEval_CallObject(id->func,arglist);     // Call Python

+#else

+      /* for python 3.9 and newer */

+      fresult = PyObject_Call(id->func,arglist,NULL);

+#endif

       Py_DECREF(id->func);

       Py_DECREF(id->data);

       free(id);

diff --git a/pythonmod/pythonmod.c b/pythonmod/pythonmod.c

index 9006429ef..040ff7051 100644

--- a/pythonmod/pythonmod.c

+++ b/pythonmod/pythonmod.c

@@ -299,7 +299,10 @@ int pythonmod_init(struct module_env* env, int id)

       PyImport_AppendInittab(SWIG_name, (void*)SWIG_init);

 #endif

       Py_Initialize();

+#if PY_MAJOR_VERSION <= 2 || (PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION <= 6)

+      /* initthreads only for python 3.6 and older */

       PyEval_InitThreads();

+#endif

       SWIG_init();

       mainthr = PyEval_SaveThread();

    }

@@ -354,6 +357,8 @@ int pythonmod_init(struct module_env* env, int id)

    /* TODO: deallocation of pe->... if an error occurs */

    if (PyRun_SimpleFile(script_py, pe->fname) < 0) {

+#if PY_MAJOR_VERSION <= 2 || (PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION < 9)

+      /* for python before 3.9 */

       log_err("pythonmod: can't parse Python script %s", pe->fname);

       /* print the error to logs too, run it again */

       fseek(script_py, 0, SEEK_SET);

@@ -369,9 +374,45 @@ int pythonmod_init(struct module_env* env, int id)

       /* ignore the NULL return of _node, it is NULL due to the parse failure

        * that we are expecting */

       (void)PyParser_SimpleParseFile(script_py, pe->fname, Py_file_input);

+#else

+      /* for python 3.9 and newer */

+      char* fstr = NULL;

+      size_t flen = 0;

+      log_err("pythonmod: can't parse Python script %s", pe->fname);

+      /* print the error to logs too, run it again */

+      fseek(script_py, 0, SEEK_END);

+      flen = (size_t)ftell(script_py);

+      fstr = malloc(flen+1);

+      if(!fstr) {

+	      log_err("malloc failure to print parse error");

+	      PyGILState_Release(gil);

+	      fclose(script_py);

+	      return 0;

+      }

+      fseek(script_py, 0, SEEK_SET);

+      if(fread(fstr, flen, 1, script_py) < 1) {

+	      log_err("file read failed to print parse error: %s: %s",

+		pe->fname, strerror(errno));

+	      PyGILState_Release(gil);

+	      fclose(script_py);

+	      free(fstr);

+	      return 0;

+      }

+      fstr[flen] = 0;

+      /* we compile the string, but do not run it, to stop side-effects */

+      /* ignore the NULL return of _node, it is NULL due to the parse failure

+       * that we are expecting */

+      (void)Py_CompileString(fstr, pe->fname, Py_file_input);

+#endif

       log_py_err();

       PyGILState_Release(gil);

       fclose(script_py);

+#if PY_MAJOR_VERSION <= 2 || (PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION < 9)

+      /* no cleanup needed for python before 3.9 */

+#else

+      /* cleanup for python 3.9 and newer */

+      free(fstr);

+#endif

       return 0;

    }

 #if PY_MAJOR_VERSION < 3

diff --git a/pythonmod/pythonmod.c b/pythonmod/pythonmod.c

index 040ff70..6e60d02 100644

--- a/pythonmod/pythonmod.c

+++ b/pythonmod/pythonmod.c

@@ -338,7 +338,7 @@ int pythonmod_init(struct module_env* env, int id)

    PyFileObject = PyFile_FromString((char*)pe->fname, "r");

    script_py = PyFile_AsFile(PyFileObject);

 #else

-   script_py = _Py_fopen(pe->fname, "r");

+   script_py = fopen(pe->fname, "r");

 #endif

    if (script_py == NULL)

    {