ERROR: testTLS (varnish_test.VarnishXcpsTest)
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Traceback (most recent call last):
  File "/home/ema/wmf/operations-puppet/modules/mtail/files/test/varnish_test.py", line 46, in setUp
    os.path.join(test_dir, 'logs/varnish.test'))
  File "/home/ema/wmf/operations-puppet/modules/mtail/files/test/mtail_store.py", line 10, in __init__
    self.parse_metric_store(self.run_mtail()[0])
  File "/home/ema/wmf/operations-puppet/modules/mtail/files/test/mtail_store.py", line 30, in parse_metric_store
    self._store = json.loads(''.join(metrics_store))
  File "/usr/lib/python2.7/json/__init__.py", line 339, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 364, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python2.7/json/decoder.py", line 382, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded