Create a `dict` of default configurations.

def _init_defaults(self):
        """Create a `dict` of default configurations."""
        defaults = {
            'build_dir': None,
            'build_datetime': datetime.datetime.now(dateutil.tz.tzutc()),
            'pdf_path': None,
            'extra_downloads': list(),
            'environment': None,
            'lsstdoc_tex_path': None,
            'title': None,
            'title_plain': "",
            'authors': None,
            'authors_json': list(),
            'doc_handle': None,
            'series': None,
            'series_name': None,
            'abstract': None,
            'abstract_plain': "",
            'ltd_product': None,
            'docushare_url': None,
            'github_slug': None,
            'git_branch': 'master',  # so we default to the main LTD edition
            'git_commit': None,
            'git_tag': None,
            'travis_job_number': None,
            'is_travis_pull_request': False,  # If not on Travis, not a PR
            'is_draft_branch': True,
            'aws_id': None,
            'aws_secret': None,
            'keeper_url': 'https://keeper.lsst.codes',
            'keeper_user': None,
            'keeper_password': None,
            'upload': False
        }
        return defaults