zodbdump: Default out to stdout in binary mode

Zodbdump format is mixed text+binary so dumping to unicode stdout won't
work.

Based on patch by Jérome Perrin.

zodbtools/util.py

@@ -20,7 +20,7 @@
 # See COPYING file for full licensing terms.
 # See https://www.nexedi.com/licensing for rationale and options.
 
-import hashlib, struct, codecs
+import hashlib, struct, codecs, io
 import zodburi
 from six.moves.urllib_parse import urlsplit, urlunsplit
 from zlib import crc32, adler32
@@ -225,3 +225,13 @@ hashRegistry = {
     "sha256":   hashlib.sha256,
     "sha512":   hashlib.sha512,
 }
+
+# ---- IO ----
+
+# asbinstream return binary stream associated with stream.
+# For example on py3 sys.stdout is io.TextIO which does not allow to write binary data to it.
+def asbinstream(stream):
+    # type: (IO) -> BinaryIO
+    if isinstance(stream, io.TextIOBase):
+        return stream.buffer
+    return stream

zodbtools/zodbdump.py

-# Copyright (C) 2016-2018  Nexedi SA and Contributors.
+# -*- coding: utf-8 -*-
+# Copyright (C) 2016-2019  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
+#                          Jérome Perrin <jerome@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
 # it under the terms of the GNU General Public License version 3, or (at your
@@ -54,7 +56,7 @@ TODO also protect txn record by hash.
 
 from __future__ import print_function
 from zodbtools.util import ashex, fromhex, sha1, txnobjv, parse_tidrange, TidRangeInvalid,   \
-        storageFromURL, hashRegistry
+        storageFromURL, hashRegistry, asbinstream
 from ZODB._compat import loads, _protocol, BytesIO
 from zodbpickle.slowpickle import Pickler as pyPickler
 #import pickletools
@@ -90,7 +92,7 @@ _already_warned_notxnraw = set()
 
 # zodbdump dumps content of a ZODB storage to a file.
 # please see module doc-string for dump format and details
-def zodbdump(stor, tidmin, tidmax, hashonly=False, out=sys.stdout):
+def zodbdump(stor, tidmin, tidmax, hashonly=False, out=asbinstream(sys.stdout)):
     for txn in stor.iterator(tidmin, tidmax):
         # XXX .status not covered by IStorageTransactionInformation
         # XXX but covered by BaseStorage.TransactionRecord