Nested augment from submodule doesn't work.

[llhotka]

The following modules lead to KeyError. They

modules.zip

should IMO work.

$ cat main.yang 
module main {
  namespace "http://example.com/main";
  prefix m;

  container top;
}
$ cat test.yang 
module test {

  namespace "http://example.com/test";

  prefix "t";

  import main {
    prefix "m";
  }

  include subtest;

  augment "/m:top" {
    container cnt {
      presence "yes";
    }
  }
}
$ cat subtest.yang 
submodule subtest {

  belongs-to test {
    prefix "t";
  }

  import main {
    prefix "m";
  }

  augment "/m:top/t:cnt" {
    leaf foo {
      mandatory "true";
      type string;
    }
  }
}
$ pyang main.yang test.yang 
Traceback (most recent call last):
  File "/Users/lhotka/bin/pyang", line 425, in <module>
    run()
  File "/Users/lhotka/bin/pyang", line 291, in run
    expect_failure_error=False)
  File "/Users/lhotka/lib/python/pyang/__init__.py", line 100, in add_module
    return self.add_parsed_module(module)
  File "/Users/lhotka/lib/python/pyang/__init__.py", line 122, in add_parsed_module
    statements.validate_module(self, module)
  File "/Users/lhotka/lib/python/pyang/statements.py", line 95, in validate_module
    iterate(module, phase)
  File "/Users/lhotka/lib/python/pyang/statements.py", line 87, in iterate
    iterate(s, phase)
  File "/Users/lhotka/lib/python/pyang/statements.py", line 52, in iterate
    res = f(ctx, stmt)
  File "/Users/lhotka/lib/python/pyang/statements.py", line 198, in <lambda>
    ('expand_2', 'augment'):lambda ctx, s: v_expand_2_augment(ctx, s),
  File "/Users/lhotka/lib/python/pyang/statements.py", line 1529, in v_expand_2_augment
    del stmt.i_module.i_undefined_augment_nodes[ch]
KeyError: <pyang.statements.Statement object at 0x10261b950>