Validating YANG: Augment target node "connect/input" in grouping "connect-grouping" was not found

[smark28]

Hi Team

I'm trying to validate yang modules with libyang and facing this error.

libyang.util.LibyangError: cannot load module: Augment target node "connect/input" in grouping "connect-grouping" was not found.

Below are truncated files, the full version of tailf-common can be found here
https://www.netconfcentral.org/src/tailf-common@2019-05-16.yang

Any help in finding the cause, I would appreciate it. Thanks

module tailf-ncs-devices {
  yang-version 1.1;
  namespace "http://tail-f.com/dev";
  prefix dev;


  import tailf-common {
    prefix tailf;
  }


  grouping connect-grouping {
    tailf:action connect {
      input {
        leaf source {
          type string;
        }
      }
    }
  }

  grouping connect-grouping-extended {
    uses connect-grouping {
      augment connect/input {
      }
    }
  }
} 

module tailf-common {
  namespace "http://tail-f.com/yang/common";
  prefix tailf;

  extension action {
  }
} 

[michalvasko]

You are targeting an extension (tailf:action) by a standard augment, it works only for standard schema nodes, no extensions.