*: Pass bytes literal into BytesIO

Otherwise it breaks with str on py3:

	In [1]: from io import BytesIO

	In [2]: BytesIO("abc")
	---------------------------------------------------------------------------
	TypeError                                 Traceback (most recent call last)
	<ipython-input-2-52a130edd46d> in <module>()
	----> 1 BytesIO("abc")

	TypeError: a bytes-like object is required, not 'str'

zodbtools/test/test_dump.py

@@ -120,7 +120,7 @@ extension "qqq"
     assert z == in_
 
     # unknown hash function
-    r = DumpReader(BytesIO("""\
+    r = DumpReader(BytesIO(b"""\
 txn 0000000000000000 " "
 user ""
 description ""
@@ -133,7 +133,7 @@ obj 0000000000000001 1 xyz:0123 -
     assert exc.value.args == ("""+5: invalid line: unknown hash function "xyz" ("obj 0000000000000001 1 xyz:0123 -")""",)
 
     # data integrity error
-    r = DumpReader(BytesIO("""\
+    r = DumpReader(BytesIO(b"""\
 txn 0000000000000000 " "
 user ""
 description ""

zodbtools/zodbcommit.py

-# Copyright (C) 2018-2019  Nexedi SA and Contributors.
+# Copyright (C) 2018-2020  Nexedi SA and Contributors.
 #                          Kirill Smelkov <kirr@nexedi.com>
 #
 # This program is free software: you can Use, Study, Modify and Redistribute
@@ -159,7 +159,7 @@ def main(argv):
     stor = storageFromURL(storurl)
     defer(stor.close)
 
-    zin = 'txn 0000000000000000 " "\n'  # artificial transaction header
+    zin = b'txn 0000000000000000 " "\n'  # artificial transaction header
     zin += sys.stdin.read()
     zin = BytesIO(zin)
     zr = zodbdump.DumpReader(zin)