Adds a hacking check looking for Logger.warn usage

Python3 has deprecated Logger.warn in favor of Logger.warning. Let's not
allow Logger.warn to be used in our codebase.

Change-Id: I271662ee8ab5f6843180cbde173aec9135ddb529
Related-Bug: #1530742

keystone/tests/hacking/checks.py

@@ -144,6 +144,7 @@ class CheckForLoggingIssues(BaseASTChecker):
     DEBUG_CHECK_DESC = 'K005 Using translated string in debug logging'
     NONDEBUG_CHECK_DESC = 'K006 Not using translating helper for logging'
     EXCESS_HELPER_CHECK_DESC = 'K007 Using hints when _ is necessary'
+    USING_DEPRECATED_WARN = 'K009 Using the deprecated Logger.warn'
     LOG_MODULES = ('logging', 'oslo_log.log')
     I18N_MODULES = (
         'keystone.i18n._',
@@ -155,7 +156,6 @@ class CheckForLoggingIssues(BaseASTChecker):
     TRANS_HELPER_MAP = {
         'debug': None,
         'info': '_LI',
-        'warn': '_LW',
         'warning': '_LW',
         'error': '_LE',
         'exception': '_LE',
@@ -294,6 +294,11 @@ class CheckForLoggingIssues(BaseASTChecker):
             else:  # could be Subscript, Call or many more
                 return super(CheckForLoggingIssues, self).generic_visit(node)
 
+            # if dealing with a logger the method can't be "warn"
+            if obj_name in self.logger_names and method_name == 'warn':
+                msg = node.args[0]  # first arg to a logging method is the msg
+                self.add_error(msg, message=self.USING_DEPRECATED_WARN)
+
             # must be a logger instance and one of the support logging methods
             if (obj_name not in self.logger_names
                     or method_name not in self.TRANS_HELPER_MAP):

keystone/tests/unit/ksfixtures/hacking.py

@@ -409,3 +409,15 @@ class HackingLogging(fixtures.Fixture):
             'expected_errors': [],
         },
     ]
+
+    assert_not_using_deprecated_warn = {
+        'code': """
+                # Logger.warn has been deprecated in Python3 in favor of
+                # Logger.warning
+                LOG = log.getLogger(__name__)
+                LOG.warn(_LW('text'))
+        """,
+        'expected_errors': [
+            (4, 9, 'K009'),
+        ],
+    }

keystone/tests/unit/test_hacking_checks.py

@@ -98,7 +98,7 @@ class TestCheckForDebugLoggingIssues(BaseStyleCheck):
         self.assert_has_errors(code, expected_errors=errors)
 
 
-class TestCheckForNonDebugLoggingIssues(BaseStyleCheck):
+class BaseLoggingCheck(BaseStyleCheck):
 
     def get_checker(self):
         return checks.CheckForLoggingIssues
@@ -106,13 +106,8 @@ class TestCheckForNonDebugLoggingIssues(BaseStyleCheck):
     def get_fixture(self):
         return hacking_fixtures.HackingLogging()
 
-    def test_for_translations(self):
-        for example in self.code_ex.examples:
-            code = self.code_ex.shared_imports + example['code']
-            errors = example['expected_errors']
-            self.assert_has_errors(code, expected_errors=errors)
-
     def assert_has_errors(self, code, expected_errors=None):
+
         # pull out the parts of the error that we'll match against
         actual_errors = (e[:3] for e in self.run_check(code))
         # adjust line numbers to make the fixture data more readable.
@@ -122,6 +117,24 @@ class TestCheckForNonDebugLoggingIssues(BaseStyleCheck):
         self.assertEqual(expected_errors or [], actual_errors)
 
 
+class TestLoggingWithWarn(BaseLoggingCheck):
+
+    def test(self):
+        data = self.code_ex.assert_not_using_deprecated_warn
+        code = self.code_ex.shared_imports + data['code']
+        errors = data['expected_errors']
+        self.assert_has_errors(code, expected_errors=errors)
+
+
+class TestCheckForNonDebugLoggingIssues(BaseLoggingCheck):
+
+    def test_for_translations(self):
+        for example in self.code_ex.examples:
+            code = self.code_ex.shared_imports + example['code']
+            errors = example['expected_errors']
+            self.assert_has_errors(code, expected_errors=errors)
+
+
 class TestDictConstructorWithSequenceCopy(BaseStyleCheck):
 
     def get_checker(self):