Unittest fails on Jenkins Build: AttributeError: 'numpy.bytes_' object has no attribute 'get'

[JackKelly]

https://travis-ci.com/github/openclimatefix/pvoutput/builds/203478127

=================================== FAILURES ===================================
_______________________ test_get_date_ranges_to_download _______________________
    def test_get_date_ranges_to_download():
        date_ranges = utils.get_date_ranges_to_download(
>           TEST_HDF, PV_SYSTEM, '2018-01-01', '2019-01-10')
pvoutput/tests/test_utils.py:36: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../../virtualenv/python3.7.1/src/pvoutput/pvoutput/utils.py:123: in get_date_ranges_to_download
    store_filename, system_id)
../../../virtualenv/python3.7.1/src/pvoutput/pvoutput/utils.py:174: in get_dates_already_downloaded
    key=key, columns=['datetime', 'query_date'])
../../../virtualenv/python3.7.1/lib/python3.7/site-packages/pandas/io/pytables.py:867: in select
    return it.get_result()
../../../virtualenv/python3.7.1/lib/python3.7/site-packages/pandas/io/pytables.py:1921: in get_result
    results = self.func(self.start, self.stop, where)
../../../virtualenv/python3.7.1/lib/python3.7/site-packages/pandas/io/pytables.py:851: in func
    return s.read(start=_start, stop=_stop, where=_where, columns=columns)
../../../virtualenv/python3.7.1/lib/python3.7/site-packages/pandas/io/pytables.py:4474: in read
    result = self._read_axes(where=where, start=start, stop=stop)
../../../virtualenv/python3.7.1/lib/python3.7/site-packages/pandas/io/pytables.py:3679: in _read_axes
    a.set_info(self.info)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
self = name->index,cname->index,axis->0,pos->0,kind->datetime64
info = b'(dp0\nI1\n(dp1\nVnames\np2\n(lp3\nNasVtype\np4\nVIndex\np5\nssVindex\np6\n(dp7\nVfreq\np8\nccopy_reg\n_reconstructor...\nsbsVindex_name\np19\nVdatetime\np20\nssVdatetime_of_API_request\np21\n(dp22\nVtz\np23\ncpytz\n_UTC\np24\n(tRp25\nss.'
    def set_info(self, info):
        """ set my state from the passed info """
>       idx = info.get(self.name)
E       AttributeError: 'numpy.bytes_' object has no attribute 'get'
../../../virtualenv/python3.7.1/lib/python3.7/site-packages/pandas/io/pytables.py:2179: AttributeError