variables from FGOALS-g2 without longitude coordinate cannot be read

[bouweandela]

The fix that is applied to all variables of the FGOALS-g2 model assumes that there is a longitude coordinate

This can be tested e.g. with recipe_ocean_amoc.yml

Traceback (most recent call last):
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/multiprocessing/pool.py", line 125, in worker
    result = (True, func(*args, **kwds))
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/_task.py", line 730, in _run_task
    output_files = task.run()
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/_task.py", line 242, in run
    self.output_files = self._run(input_files)
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/preprocessor/__init__.py", line 428, in _run
    product.apply(step, self.debug)
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/preprocessor/__init__.py", line 296, in apply
    self.cubes = preprocess(self.cubes, step, **self.settings[step])
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/preprocessor/__init__.py", line 238, in preprocess
    result.append(_run_preproc_function(function, items, settings))
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/preprocessor/__init__.py", line 224, in _run_preproc_function
    return function(items, **kwargs)
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/cmor/fix.py", line 107, in fix_metadata
    cube_list = fix.fix_metadata(cube_list)
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/cmor/_fixes/cmip5/fgoals_g2.py", line 36, in fix_metadata
    round_coordinates(cubes, 4, coord_names=['longitude'])
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/cmor/_fixes/shared.py", line 446, in round_coordinates
    coords = [cube.coord(name) for name in coord_names]
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/esmvalcore/cmor/_fixes/shared.py", line 446, in <listcomp>
    coords = [cube.coord(name) for name in coord_names]
  File "/work/bd0080/b309057/SOFTWARE/miniconda3/envs/esmvaltool/lib/python3.8/site-packages/iris/cube.py", line 1497, in coord
    raise iris.exceptions.CoordinateNotFoundError(msg)
iris.exceptions.CoordinateNotFoundError: 'Expected to find exactly 1 longitude coordinate, but found none.'

[valeriupredoi]

yeah I've seen a few such cases in multiple fixes scripts - these need to be fixed (I should have opened an issue right there and then when I saw them) 🍺