Added hacking check to ensure LOG.warn is not used

LOG.warn is deprecated. To ensure it is not used later
added hacking check.

Change-Id: Iadd1d4f4588c9d47baefd685a97a73c8b1aee987
Closes-Bug: #1605711

HACKING.rst

@@ -23,3 +23,4 @@ Magnum Specific Commandments
   with a sequence of key-value pairs.
 - [M338] Use assertIn/NotIn(A, B) rather than assertEqual(A in B, True/False).
 - [M339] Don't use xrange()
+- [M352] LOG.warn is deprecated. Enforce use of LOG.warning.

magnum/hacking/checks.py

@@ -144,6 +144,20 @@ def dict_constructor_with_list_copy(logical_line):
         yield (0, msg)
 
 
+def no_log_warn(logical_line):
+    """Disallow 'LOG.warn('
+
+    Deprecated LOG.warn(), instead use LOG.warning
+    https://bugs.launchpad.net/magnum/+bug/1508442
+
+    M352
+    """
+
+    msg = ("M352: LOG.warn is deprecated, please use LOG.warning!")
+    if "LOG.warn(" in logical_line:
+        yield (0, msg)
+
+
 def factory(register):
     register(no_mutable_default_args)
     register(assert_equal_none)
@@ -154,3 +168,4 @@ def factory(register):
     register(use_timeutils_utcnow)
     register(dict_constructor_with_list_copy)
     register(no_xrange)
+    register(no_log_warn)

magnum/tests/unit/test_hacking.py

@@ -189,6 +189,19 @@ class HackingTestCase(base.TestCase):
         code = "range(45)"
         self._assert_has_no_errors(code, check)
 
+    def test_no_log_warn(self):
+        errors = [(1, 0, "M352")]
+        check = checks.no_log_warn
+        code = """
+                  LOG.warn("LOG.warn is deprecated")
+               """
+        self._assert_has_errors(code, check, errors)
+
+        code = """
+                  LOG.warning("LOG.warn is deprecated")
+               """
+        self._assert_has_no_errors(code, check)
+
     def test_use_timeunitls_utcow(self):
         errors = [(1, 0, "M310")]
         check = checks.use_timeutils_utcnow