pycsp: Release Py_Buffers after use

The documentation for `w*` specifies that
> The caller have to call PyBuffer_Release() when it is done with the buffer.

https://docs.python.org/3/c-api/arg.html

src/bindings/python/pycsp.c

@@ -270,11 +270,12 @@ static PyObject* pycsp_transaction(PyObject *self, PyObject *args) {
     Py_BEGIN_ALLOW_THREADS;
     res = csp_transaction(prio, dest, port, timeout, outbuf.buf, outbuf.len, inbuf.buf, inbuf.len);
     Py_END_ALLOW_THREADS;
-    if (res < 1) {
-        return PyErr_Error("csp_transaction()", res);
-    }
 
-    return Py_BuildValue("i", res);
+    PyBuffer_Release(&inbuf);
+    PyBuffer_Release(&outbuf);
+    return res < 1
+        ? PyErr_Error("csp_transaction()", res)
+        : Py_BuildValue("i", res);
 }
 
 static PyObject* pycsp_sendto(PyObject *self, PyObject *args) {
@@ -694,6 +695,7 @@ static PyObject* pycsp_cmp_peek(PyObject *self, PyObject *args) {
     }
 
     if ((len > CSP_CMP_PEEK_MAX_LEN) || (len > outbuf.len)) {
+        PyBuffer_Release(&outbuf);
         return PyErr_Error("csp_cmp_peek() - exceeding max size", CSP_ERR_INVAL);
     }
 
@@ -707,11 +709,13 @@ static PyObject* pycsp_cmp_peek(PyObject *self, PyObject *args) {
     res = csp_cmp_peek(node, timeout, &msg);
     Py_END_ALLOW_THREADS;
     if (res != CSP_ERR_NONE) {
+        PyBuffer_Release(&outbuf);
         return PyErr_Error("csp_cmp_peek()", res);
     }
     memcpy(outbuf.buf, msg.peek.data, len);
     outbuf.len = len;
 
+    PyBuffer_Release(&outbuf);
     Py_RETURN_NONE;
 }
 
@@ -727,6 +731,7 @@ static PyObject* pycsp_cmp_poke(PyObject *self, PyObject *args) {
     }
 
     if (len > CSP_CMP_POKE_MAX_LEN) {
+        PyBuffer_Release(&inbuf);
         return PyErr_Error("csp_cmp_poke() - exceeding max size", CSP_ERR_INVAL);
     }
     struct csp_cmp_message msg;
@@ -739,9 +744,11 @@ static PyObject* pycsp_cmp_poke(PyObject *self, PyObject *args) {
     res = csp_cmp_poke(node, timeout, &msg);
     Py_END_ALLOW_THREADS;
     if (res != CSP_ERR_NONE) {
+        PyBuffer_Release(&inbuf);
         return PyErr_Error("csp_cmp_poke()", res);
     }
 
+    PyBuffer_Release(&inbuf);
     Py_RETURN_NONE;
 }
 
@@ -945,15 +952,18 @@ static PyObject* pycsp_packet_set_data(PyObject *self, PyObject *args) {
 
     csp_packet_t * packet = get_obj_as_packet(packet_capsule, false);
     if (packet == NULL) {
+        PyBuffer_Release(&data);
         return NULL; // TypeError is thrown
     }
     if (data.len > (int)csp_buffer_data_size()) {
+        PyBuffer_Release(&data);
         return PyErr_Error("packet_set_data() - exceeding data size", CSP_ERR_INVAL);
     }
 
     memcpy(packet->data, data.buf, data.len);
     packet->length = data.len;
 
+    PyBuffer_Release(&data);
     Py_RETURN_NONE;
 }