test_fillvalue.py failed

[dnadeau4]

fill_value is not retain when writing a variable to a file.

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FAIL: testWriteFillValue (__main__.TestFillValueWrite)
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Traceback (most recent call last):
  File "test_fillvalue.py", line 60, in testWriteFillValue
    self.assertTrue(all([v == 1.33 for v in (m.fill_value, m._FillValue, m.missing_value)]))
AssertionError: False is not true

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