TypeError trying to modify comment with yaml_add_eol_comment

[tompaton]

Using version ruyaml==0.19.2 (issue also occurred with master).

Generate a test file:

Python 3.7.2 (default, Mar  5 2019, 06:22:51)
[GCC 6.3.0 20170516] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from ruamel.yaml import YAML
>>> data = {'items': [{'one': 1, 'uno': '1'}, {'two': 2, 'duo': '2'}, {'three': 3}]}
>>> yaml = YAML(typ='rt')
>>> yaml.dump(data, stream=open('input.yaml', 'w'))
>>> print(open('input.yaml', 'r').read())
items:
- one: 1
  uno: '1'
- two: 2
  duo: '2'
- three: 3

Read the file and add a comment, this works as expected:

>>> yaml = YAML(typ='rt')
>>> data = yaml.load(open('input.yaml', 'r'))
>>> data['items'].yaml_add_eol_comment('item 2', key=1)
>>> yaml = YAML(typ='rt')
>>> yaml.dump(data, stream=open('output.yaml', 'w'))
>>> print(open('output.yaml', 'r').read())
items:
- one: 1
  uno: '1'
-  # item 2
  two: 2
  duo: '2'
- three: 3

But if I read that file back in and try to change the comment, there is an error:

>>> yaml = YAML(typ='rt')
>>> data = yaml.load(open('output.yaml', 'r'))
>>> data['items'].yaml_add_eol_comment('second pass', key=1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.7/site-packages/ruamel/yaml/comments.py", line 303, in yaml_add_eol_comment
    self._yaml_add_eol_comment(ct, key=key)
  File "/usr/local/lib/python3.7/site-packages/ruamel/yaml/comments.py", line 441, in _yaml_add_eol_comment
    self._yaml_add_comment(comment, key=key)
  File "/usr/local/lib/python3.7/site-packages/ruamel/yaml/comments.py", line 435, in _yaml_add_comment
    self.yaml_key_comment_extend(key, comment)
  File "/usr/local/lib/python3.7/site-packages/ruamel/yaml/comments.py", line 206, in yaml_key_comment_extend
    r[1].extend(comment[0])
TypeError: 'CommentToken' object is not iterable

Note, this works ok with a simpler input file, e.g.:

items:
- one
- two
- three

[ssbarnea]

PRs are welcomed!

[tompaton]

I looked into it when trying to reproduce it, but I'm no where near familiar enough with the code to understand what's going on, let along know what needs to be done to fix this I'm afraid...

[tompaton]

I think I managed to fix this issue in PR #35