log: expose ly_temp_log_options with a context manager

When one wishes to disable logging temporarily (e.g., when calling API functions
when an error result is expected and OK), libyang provides
ly_temp_log_options(). We need access to this in python, so export access to the
function and add a python context (i.e., "with") manager API for using
it idiomatically as well.

ex usage:

```
    with temp_log_options(0):
        ly_unwanted_logging_call();
```

Signed-off-by: Christian Hopps <[email protected]>

Author: choppsv1

cffi/cdefs.h

@@ -182,6 +182,7 @@ enum ly_stmt {
 #define LY_LOSTORE ...
 #define LY_LOSTORE_LAST ...
 int ly_log_options(int);
+uint32_t *ly_temp_log_options(uint32_t *);
 
 LY_LOG_LEVEL ly_log_level(LY_LOG_LEVEL);
 extern "Python" void lypy_log_cb(LY_LOG_LEVEL, const char *, const char *, const char *, uint64_t);

libyang/__init__.py

@@ -65,7 +65,7 @@
 )
 from .extension import ExtensionPlugin, LibyangExtensionError
 from .keyed_list import KeyedList
-from .log import configure_logging
+from .log import configure_logging, temp_log_options
 from .schema import (
     Extension,
     ExtensionCompiled,

libyang/log.py

@@ -2,8 +2,11 @@
 # Copyright (c) 2020 6WIND S.A.
 # SPDX-License-Identifier: MIT
 
+from contextlib import contextmanager
 import logging
 
+import cffi
+
 from _libyang import ffi, lib
 from .util import c2str
 
@@ -26,6 +29,16 @@ def get_libyang_level(py_level):
     return None
 
 
+@contextmanager
+def temp_log_options(opt: int = 0):
+    _ffi = cffi.FFI()
+    opts = _ffi.new("uint32_t *", opt)
+
+    lib.ly_temp_log_options(opts)
+    yield
+    lib.ly_temp_log_options(ffi.NULL)
+
+
 @ffi.def_extern(name="lypy_log_cb")
 def libyang_c_logging_callback(level, msg, data_path, schema_path, line):
     args = [c2str(msg)]