[Bug] The `test_iodaconv_airnow_epalist` test fails

[fabiolrdiniz]

Despite the warnings, a few different values are assigned for the /MetaData/airQualityClassification variable (see below):

/home/fabiodiniz/jedi-bundle/build/bin/airnow2ioda_nc.py:132: FutureWarning: 'H' is deprecated and will be removed in a future version. Please use 'h' instead of 'H'.
  df['time_local'] = df.time + pd.to_timedelta(df.utcoffset, unit='H')
/home/fabiodiniz/jedi-bundle/build/bin/airnow2ioda_nc.py:217: FutureWarning: The behavior of DatetimeProperties.to_pydatetime is deprecated, in a future version this will return a Series containing python datetime objects instead of an ndarray. To retain the old behavior, call `np.array` on the result
  f3['time'] = f3['time'].dt.to_pydatetime()
/home/fabiodiniz/jedi/spack-stack/spack-stack-1.9.0/envs/unified-dev/install/gcc/13.3.0/py-pandas-2.2.3-zhm5kf7/lib/python3.11/site-packages/pandas/core/series.py:1031: RuntimeWarning: invalid value encountered in cast
  arr = np.asarray(values, dtype=dtype)
sitefile= testinput/airnow_sites_epalist_20240716.csv
Processing infile= testinput/airnow_2020081306.dat
DIFFER : VARIABLE : airQualityClassification : POSITION : [108] : VALUES : 0 <> -2147483648 : PERCENT : 100
DIFFER : VARIABLE : airQualityClassification : POSITION : [146] : VALUES : 0 <> -2147483648 : PERCENT : 100
DIFFER : VARIABLE : airQualityClassification : POSITION : [882] : VALUES : 0 <> -2147483648 : PERCENT : 100
DIFFER : VARIABLE : airQualityClassification : POSITION : [1414] : VALUES : 0 <> -2147483648 : PERCENT : 100
Variable                 Group     Count         Sum      AbsSum         Min         Max Range        Mean StdDev
airQualityClassification /MetaData     4 8.58993e+09 8.58993e+09 2.14748e+09 2.14748e+09     0 2.14748e+09      0

[fabiolrdiniz]

Important to mention, -2147483647 is the missing value for an integer.

[fabiolrdiniz]

I'm convinced the error is in the reference. Opening a PR with new reference now.