NetCDF writer doesn't work

[pnuu]

Code Sample, a minimal, complete, and verifiable piece of code

from satpy import Scene
from satpy.utils import debug_on
import glob

debug_on()
fnames = glob.glob("/home/lahtinep/data/satellite/viirs/*b30342*")
glbl = Scene(reader="viirs_sdr", filenames=fnames)
glbl.load(['I05'])
lcl = glbl.resample('euro4')

# This works
lcl.save_datasets(writer='geotiff', filename='/tmp/foo.tif')

# This doesn't
lcl.save_datasets(writer='cf', filename='/tmp/foo.nc')

Problem description

As seen from the trace below, the NetCDF writer uses cf.Domain which seems to be removed from the cf-python package, and therefore fails to save the data.

Actual Result, Traceback if applicable

[INFO: 2017-12-12 08:14:04 : satpy.writers.cf_writer] Saving datasets to NetCDF4/CF.
[INFO: 2017-12-12 08:14:04 : satpy.writers.cf_writer] No longitude and latitude data to save.
[INFO: 2017-12-12 08:14:04 : satpy.writers.cf_writer] No grid mapping to save.
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-24-58ece08c15f3> in <module>()
----> 1 lcl.save_datasets(writer='cf', filename='/tmp/foo.nc')

/home/lahtinep/Software/pytroll/packages/satpy/satpy/scene.pyc in save_datasets(self, writer, datasets, **kwargs)
    632             datasets = self.datasets.values()
    633         writer = self.get_writer(writer, **kwargs)
--> 634         writer.save_datasets(datasets, **kwargs)
    635 
    636     def get_writer(self, writer="geotiff", **kwargs):

/home/lahtinep/Software/pytroll/packages/satpy/satpy/writers/cf_writer.pyc in save_datasets(self, datasets, filename, **kwargs)
    176                     coords = [line_coord, pixel_coord]
    177 
--> 178                 domain = cf.Domain(dim=coords,
    179                                    aux=aux,
    180                                    ref=grid_mapping)

AttributeError: 'module' object has no attribute 'Domain'

Versions of Python, package at hand and relevant dependencies

SatPy 0.7.5, cf-python 2.1.2, Python 2.7.12

[mraspaud]

cf-python is broken, so this version of the cf-writer is broken too. A fix is implemented in PR #83 .