update with Maxim's suggestion

Author: zkamvar

bin/lesson_check.py

@@ -188,10 +188,9 @@ def check_config(reporter, source_dir):
         reporter.check(defaults in config.get('defaults', []),
                    'configuration',
                    '"root" not set to "." in configuration')
-    if 'life_cycle' in config:
-        return config['life_cycle']
-    else
-        return None
+    if 'life_cycle' not in config:
+        config['life_cycle'] = None
+    return config['life_cycle']
 
 def check_source_rmd(reporter, source_dir, parser):
     """Check that Rmd episode files include `source: Rmd`"""