patch msgpack to use relative imports

patch by felix schwarz, thanks!

src/borg/_msgpack/__init__.py

@@ -1,6 +1,6 @@
 # coding: utf-8
-from msgpack._version import version
-from msgpack.exceptions import *
+from ._version import version
+from .exceptions import *
 
 from collections import namedtuple
 
@@ -19,13 +19,13 @@ class ExtType(namedtuple('ExtType', 'code data')):
 
 import os
 if os.environ.get('MSGPACK_PUREPYTHON'):
-    from msgpack.fallback import Packer, unpackb, Unpacker
+    from .fallback import Packer, unpackb, Unpacker
 else:
     try:
-        from msgpack._packer import Packer
-        from msgpack._unpacker import unpackb, Unpacker
+        from ._packer import Packer
+        from ._unpacker import unpackb, Unpacker
     except ImportError:
-        from msgpack.fallback import Packer, unpackb, Unpacker
+        from .fallback import Packer, unpackb, Unpacker
 
 
 def pack(o, stream, **kwargs):

src/borg/_msgpack/_packer.pyx

@@ -5,8 +5,8 @@ from cpython cimport *
 from cpython.version cimport PY_MAJOR_VERSION
 from cpython.exc cimport PyErr_WarnEx
 
-from msgpack.exceptions import PackValueError, PackOverflowError
-from msgpack import ExtType
+from .exceptions import PackValueError, PackOverflowError
+from . import ExtType
 
 
 cdef extern from "Python.h":

src/borg/_msgpack/_unpacker.pyx

@@ -32,13 +32,13 @@ from libc.string cimport *
 from libc.limits cimport *
 ctypedef unsigned long long uint64_t
 
-from msgpack.exceptions import (
+from .exceptions import (
     BufferFull,
     OutOfData,
     UnpackValueError,
     ExtraData,
 )
-from msgpack import ExtType
+from . import ExtType
 
 
 cdef extern from "unpack.h":

src/borg/_msgpack/fallback.py

@@ -49,7 +49,7 @@ else:
     newlist_hint = lambda size: []
 
 
-from msgpack.exceptions import (
+from .exceptions import (
     BufferFull,
     OutOfData,
     UnpackValueError,
@@ -57,7 +57,7 @@ from msgpack.exceptions import (
     PackOverflowError,
     ExtraData)
 
-from msgpack import ExtType
+from . import ExtType
 
 
 EX_SKIP                 = 0

src/borg/_msgpack/unpack_define.h

@@ -18,7 +18,7 @@
 #ifndef MSGPACK_UNPACK_DEFINE_H__
 #define MSGPACK_UNPACK_DEFINE_H__
 
-#include "msgpack/sysdep.h"
+#include "sysdep.h"
 #include <stdlib.h>
 #include <string.h>
 #include <assert.h>