Add hacking checks for xrange()

Partially-Implements: blueprint goal-python35

Change-Id: Iea2e9e5d5782b898ba5b18314745962cc059a213

HACKING.rst

@@ -37,6 +37,7 @@ Nova Specific Commandments
 - [N324] Ensure that jsonutils.%(fun)s must be used instead of json.%(fun)s
 - [N325] str() and unicode() cannot be used on an exception.  Remove use or use six.text_type()
 - [N326] Translated messages cannot be concatenated.  String should be included in translated message.
+- [N327] Do not use xrange(). xrange() is not compatible with Python 3. Use range() or six.moves.range() instead.
 - [N328] Validate that LOG.info messages use _LI.
 - [N329] Validate that LOG.exception messages use _LE.
 - [N330] Validate that LOG.warning and LOG.warn messages use _LW.

nova/hacking/checks.py

@@ -290,6 +290,12 @@ def assert_equal_none(logical_line):
                "sentences not allowed")
 
 
+def check_python3_xrange(logical_line):
+    if re.search(r"\bxrange\s*\(", logical_line):
+        yield(0, "N327: Do not use xrange(). 'xrange()' is not compatible "
+              "with Python 3. Use range() or six.moves.range() instead.")
+
+
 def no_translate_debug_logs(logical_line, filename):
     """Check for 'LOG.debug(_('
 
@@ -793,6 +799,7 @@ def factory(register):
     register(check_python3_no_iteritems)
     register(check_python3_no_iterkeys)
     register(check_python3_no_itervalues)
+    register(check_python3_xrange)
     register(no_os_popen)
     register(no_log_warn)
     register(CheckForUncalledTestClosure)

nova/tests/unit/test_hacking.py

@@ -749,3 +749,10 @@ class HackingTestCase(test.NoDBTestCase):
         foo.enforce()
         """
         self._assert_has_no_errors(code, checks.check_policy_enforce)
+
+    def test_check_python3_xrange(self):
+        func = checks.check_python3_xrange
+        self.assertEqual(1, len(list(func('for i in xrange(10)'))))
+        self.assertEqual(1, len(list(func('for i in xrange    (10)'))))
+        self.assertEqual(0, len(list(func('for i in range(10)'))))
+        self.assertEqual(0, len(list(func('for i in six.moves.range(10)'))))