py3: Ensure cmp() is available where it is used

src/calibre/db/backend.py

@@ -13,7 +13,7 @@ from functools import partial
 
 import apsw
 from polyglot.builtins import (iteritems, itervalues,
-        unicode_type, reraise, string_or_bytes)
+        unicode_type, reraise, string_or_bytes, cmp)
 
 from calibre import isbytestring, force_unicode, prints, as_unicode
 from calibre.constants import (iswindows, filesystem_encoding,

src/calibre/devices/kobo/books.py

@@ -15,7 +15,7 @@ from calibre.devices.usbms.books import CollectionsBookList
 from calibre.utils.config_base import prefs
 from calibre.devices.usbms.driver import debug_print
 from calibre.ebooks.metadata import author_to_author_sort
-from polyglot.builtins import unicode_type, string_or_bytes, iteritems, itervalues
+from polyglot.builtins import unicode_type, string_or_bytes, iteritems, itervalues, cmp
 
 
 class Book(Book_):

src/calibre/devices/usbms/books.py

@@ -15,7 +15,7 @@ from calibre.constants import preferred_encoding
 from calibre import isbytestring, force_unicode
 from calibre.utils.config_base import tweaks
 from calibre.utils.icu import sort_key
-from polyglot.builtins import string_or_bytes, iteritems, itervalues
+from polyglot.builtins import string_or_bytes, iteritems, itervalues, cmp
 
 
 class Book(Metadata):

src/calibre/ebooks/snb/snbfile.py

@@ -8,7 +8,7 @@ __docformat__ = 'restructuredtext en'
 import sys, struct, zlib, bz2, os
 
 from calibre import guess_type
-from polyglot.builtins import unicode_type
+from polyglot.builtins import unicode_type, cmp
 
 
 class FileStream:

src/calibre/library/caches.py

@@ -21,7 +21,7 @@ from calibre.ebooks.metadata import title_sort, author_to_author_sort
 from calibre.ebooks.metadata.opf2 import metadata_to_opf
 from calibre import prints, force_unicode
 from polyglot.builtins import (iteritems, itervalues, map,
-        unicode_type, string_or_bytes, zip)
+        unicode_type, string_or_bytes, zip, cmp)
 
 
 class MetadataBackup(Thread):  # {{{

src/calibre/library/sqlite.py

@@ -20,7 +20,7 @@ from calibre import isbytestring, force_unicode
 from calibre.constants import iswindows, DEBUG, plugins
 from calibre.utils.icu import sort_key
 from calibre import prints
-from polyglot.builtins import unicode_type
+from polyglot.builtins import unicode_type, cmp
 from polyglot import reprlib
 from polyglot.queue import Queue
 

src/calibre/utils/icu.py

@@ -16,9 +16,10 @@ import codecs
 
 from calibre.constants import plugins
 from calibre.utils.config_base import tweaks
-from polyglot.builtins import unicode_type
+from polyglot.builtins import unicode_type, cmp
 
 _locale = _collator = _primary_collator = _sort_collator = _numeric_collator = _case_sensitive_collator = None
+cmp
 
 _none = u''
 _none2 = b''

src/calibre/utils/icu_test.py

@@ -10,7 +10,7 @@ import unittest, sys
 from contextlib import contextmanager
 
 import calibre.utils.icu as icu
-from polyglot.builtins import iteritems, unicode_type
+from polyglot.builtins import iteritems, unicode_type, cmp
 
 
 @contextmanager