WARNING: [doc-tree]: (invalid-page-metadata): /home/meh/devel/test_hotdoc/markdown_files/gi-index.markdown: Invalid metadata:
Key 'extra-copyrights' error:
Or({'name': And(<class 'str'>, <built-in function len>), Optional('email'): And(<class 'str'>, <built-in function len>), Optional('years'): Schema([Use(<class 'int'>)])}) did not validate {'name': 'Aperture Science', 'email': 'aperture@valve.com', 'years': None}
Key 'years' error:
None should be instance of 'list', discarding all metadata
{'short-description': 'GObject-introspected API', 'authors': [{'name': 'Mathieu Duponchelle', 'email': 'mathieu.duponchelle@opencreed.com', 'years': [2015, 2016]}], 'extra-copyrights': [{'name': 'Aperture Science', 'email': 'aperture@valve.com', 'years': None}], 'license': 'CC-BY-SA'}
An unknown error happened while building the documentation and hotdoc cannot recover from it. Please report a bug with this error message and the steps to reproduce it
Traceback (most recent call last):
  File "/home/meh/devel/hotdoc/hotdoc/run_hotdoc.py", line 318, in execute_command
    res = app.run()
  File "/home/meh/devel/hotdoc/hotdoc/run_hotdoc.py", line 113, in run
    self.project.format(self.link_resolver, self.output)
  File "/home/meh/devel/hotdoc/hotdoc/core/project.py", line 223, in format
    self.tree.format(link_resolver, output, self.extensions)
  File "/home/meh/devel/hotdoc/hotdoc/core/tree.py", line 721, in format
    self.format_page(page, link_resolver, output, extensions)
  File "/home/meh/devel/hotdoc/hotdoc/core/tree.py", line 706, in format_page
    extension.format_page(page, link_resolver, output)
  File "/home/meh/devel/hotdoc/hotdoc/extensions/gi/gi_extension.py", line 171, in format_page
    Extension.format_page (self, page, link_resolver, output)
  File "/home/meh/devel/hotdoc/hotdoc/core/extension.py", line 560, in format_page
    page.format(self.formatter, link_resolver, actual_output)
  File "/home/meh/devel/hotdoc/hotdoc/core/tree.py", line 302, in format
    formatter.format_page(self)[0]
  File "/home/meh/devel/hotdoc/hotdoc/core/formatter.py", line 299, in format_page
    self.formatting_page_signal(self, page)
  File "/home/meh/devel/hotdoc/hotdoc/utils/signals.py", line 69, in __call__
    res = func(*args, **kargs)
  File "/home/meh/devel/hotdoc/hotdoc/utils/signals.py", line 52, in __call__
    return self.func(*_args, **kwargs)
  File "/home/meh/devel/hotdoc/hotdoc/extensions/license/license_extension.py", line 197, in __formatting_page_cb
    copyrights = self.__copyrights_for_page(page)
  File "/home/meh/devel/hotdoc/hotdoc/extensions/license/license_extension.py", line 172, in __copyrights_for_page
    self.__extra_copyrights_for_page(page))
  File "/home/meh/devel/hotdoc/hotdoc/extensions/license/license_extension.py", line 165, in __extra_copyrights_for_page
    [str(year) for year in data.get('years')],
TypeError: 'NoneType' object is not iterable