Set one parameter to be type path

lib/ansible/modules/system/sysctl.py

@@ -348,7 +348,7 @@ def main():
             reload = dict(default=True, type='bool'),
             sysctl_set = dict(default=False, type='bool'),
             ignoreerrors = dict(default=False, type='bool'),
-            sysctl_file = dict(default='/etc/sysctl.conf')
+            sysctl_file = dict(default='/etc/sysctl.conf', type='path')
         ),
         supports_check_mode=True
     )
@@ -359,4 +359,5 @@ def main():
 
 # import module snippets
 from ansible.module_utils.basic import *
+if __name__ == '__main__':
     main()