py3: use pycompat.xrange instead of xrange

xrange does not exists on Python 3.

Differential Revision: https://phab.mercurial-scm.org/D5302

tests/test-remotefilelog-histpack.py

@@ -251,7 +251,7 b' class histpacktests(unittest.TestCase):'
         This causes it to use a 2^16 fanout table instead."""
         total = basepack.SMALLFANOUTCUTOFF + 1
         revisions = []
-        for i in xrange(total):
+        for i in pycompat.xrange(total):
             filename = b"foo-%d" % i
             node = self.getFakeHash()
             p1 = self.getFakeHash()