LOG_LEVELS_BY_NUM shouldn't include builtins.

src/supervisor/loggers.py

@@ -48,7 +48,8 @@ class LevelsByDescription:
 def _levelNumbers():
     bynumber = {}
     for name, number in LevelsByName.__dict__.items():
-        bynumber[number] = name
+        if not name.startswith('_'):
+            bynumber[number] = name
     return bynumber
 
 LOG_LEVELS_BY_NUM = _levelNumbers()

src/supervisor/tests/test_loggers.py

@@ -6,6 +6,12 @@ import os
 
 from supervisor.tests.base import DummyStream
 
+class LevelTests(unittest.TestCase):
+    def test_LOG_LEVELS_BY_NUM_doesnt_include_builtins(self):
+        from supervisor import loggers
+        for level_name in loggers.LOG_LEVELS_BY_NUM.values():
+            self.assertFalse(level_name.startswith('_'))
+
 class HandlerTests:
     def setUp(self):
         self.basedir = tempfile.mkdtemp()