*: Support ZODB6

ZODB6 no longer have ZODB._compat.BytesIO , manage this compatibility
layer ourselves.

--------
kirr: ZODB dropped ZODB._compat.BytesIO in https://github.com/zopefoundation/ZODB/commit/6f887812.

/reviewed-by @kirr
/reviewed-on !30

zodbtools/test/test_commit.py

@@ -21,9 +21,9 @@
 
 from zodbtools.zodbcommit import zodbcommit
 from zodbtools.zodbdump import zodbdump, Transaction, ObjectData, ObjectDelete, ObjectCopy
-from zodbtools.util import storageFromURL, sha1, ashex, fromhex
+from zodbtools.util import storageFromURL, sha1, ashex, fromhex, BytesIO
 from ZODB.utils import p64, u64, z64
-from ZODB._compat import BytesIO, dumps, _protocol   # XXX can't yet commit with arbitrary ext.bytes
+from ZODB._compat import dumps, _protocol   # XXX can't yet commit with arbitrary ext.bytes
 
 from golang import func, defer, b
 from golang.gcompat import qq

zodbtools/util.py

@@ -22,11 +22,18 @@
 
 import hashlib, struct, codecs, io
 import zodburi
+import six
 from six.moves.urllib_parse import urlsplit, urlunsplit
 from zlib import crc32, adler32
 from ZODB.TimeStamp import TimeStamp
 import dateparser
 
+# BBB Re-export BytesIO for PY2 compatibility
+if six.PY2:
+    from ZODB._compat import BytesIO
+else:
+    from io import BytesIO
+
 from golang import b
 
 

zodbtools/zodbcommit.py

@@ -40,11 +40,10 @@ can query current database head (last_tid) with `zodb info <stor> last_tid`.
 
 from __future__ import print_function
 from zodbtools import zodbdump
-from zodbtools.util import ashex, fromhex, storageFromURL, asbinstream
+from zodbtools.util import ashex, fromhex, storageFromURL, asbinstream, BytesIO
 from ZODB.interfaces import IStorageRestoreable
 from ZODB.utils import p64, u64, z64
 from ZODB.POSException import POSKeyError
-from ZODB._compat import BytesIO
 from golang import func, defer, panic, b
 import warnings
 

zodbtools/zodbdump.py

@@ -64,8 +64,8 @@ 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, asbinstream
-from ZODB._compat import loads, _protocol, BytesIO
+        storageFromURL, hashRegistry, asbinstream, BytesIO
+from ZODB._compat import loads, _protocol
 from zodbpickle.slowpickle import Pickler as pyPickler
 from ZODB.interfaces import IStorageTransactionInformation
 from zope.interface import implementer