Change the date key to non-unicode in the test fixture.
from collections import OrderedDict
from elifetools.utils import date_struct


expected = [
    OrderedDict([
        ('event_type', 'preprint-publication'),
        ('event_desc', 'This article was originally published as a <ext-link ext-link-type="uri" xlink:href="https://www.biorxiv.org/content/early/2017/03/24/118356">preprint on Biorxiv</ext-link>'),
        ('event_desc_html', 'This article was originally published as a <a href="https://www.biorxiv.org/content/early/2017/03/24/118356">preprint on Biorxiv</a>'),
        ('uri', 'https://www.biorxiv.org/content/early/2017/03/24/118356'),
        ('uri_text', 'preprint on Biorxiv'),
        ('day', '24'),
        ('month', '03'),
        ('year', '2017'),
        ('date', date_struct(2017, 3, 24)),
        ('iso-8601-date', '2017-03-24')
        ])
    ]

from collections import OrderedDict
from elifetools.utils import date_struct


expected = [
    OrderedDict([
        ('event_type', 'preprint-publication'),
        ('event_desc', 'This article was originally published as a <ext-link ext-link-type="uri" xlink:href="https://www.biorxiv.org/content/early/2017/03/24/118356">preprint on Biorxiv</ext-link>'),
        ('event_desc_html', 'This article was originally published as a <a href="https://www.biorxiv.org/content/early/2017/03/24/118356">preprint on Biorxiv</a>'),
        ('uri', 'https://www.biorxiv.org/content/early/2017/03/24/118356'),
        ('uri_text', 'preprint on Biorxiv'),
        ('day', '24'),
        ('month', '03'),
        ('year', '2017'),
        (u'date', date_struct(2017, 3, 24)),
        ('iso-8601-date', '2017-03-24')
        ])
    ]
