fallback: Fix warning stacklevel (#327)

Author: methane

msgpack/fallback.py

@@ -89,7 +89,7 @@ def _get_data_from_buffer(obj):
             warnings.warn("using old buffer interface to unpack %s; "
                           "this leads to unpacking errors if slicing is used and "
                           "will be removed in a future version" % type(obj),
-                          RuntimeWarning)
+                          RuntimeWarning, stacklevel=3)
         else:
             raise
     if view.itemsize != 1:
@@ -100,7 +100,7 @@ def _get_data_from_buffer(obj):
 def unpack(stream, **kwargs):
     warnings.warn(
         "Direct calling implementation's unpack() is deprecated, Use msgpack.unpack() or unpackb() instead.",
-        DeprecationWarning)
+        DeprecationWarning, stacklevel=2)
     data = stream.read()
     return unpackb(data, **kwargs)
 
@@ -226,7 +226,7 @@ def __init__(self, file_like=None, read_size=0, use_list=True, raw=True,
         if encoding is not None:
             warnings.warn(
                 "encoding is deprecated, Use raw=False instead.",
-                DeprecationWarning)
+                DeprecationWarning, stacklevel=2)
 
         if unicode_errors is None:
             unicode_errors = 'strict'
@@ -712,7 +712,7 @@ def __init__(self, default=None, encoding=None, unicode_errors=None,
         else:
             warnings.warn(
                 "encoding is deprecated, Use raw=False instead.",
-                DeprecationWarning)
+                DeprecationWarning, stacklevel=2)
 
         if unicode_errors is None:
             unicode_errors = 'strict'