cf.read fails for some PP data with a single vertical level

[davidhassell]

cf.read fails for some PP data with a single vertical level, as follows:

>>> import cf
>>> f = cf.read('xolaha@pas80ag.pp')
<snip>
File ~/cf-python/cf/read_write/um/umread.py:2004, in UMField.create_data(self)
   2001 indices = [(i, rec) for i, rec in enumerate(recs)]
   2003 if z_axis in self.down_axes:
-> 2004     indices = self._reorder_z_axis(indices, z_axis, pmaxes)
   2006 for i, rec in indices:
   2007     # Find the data type of the array in the file
   2008     file_data_type = data_type_in_file(rec)

File ~/cf-python/cf/read_write/um/umread.py:1173, in UMField._reorder_z_axis(self, indices, z_axis, pmaxes)
   1139 """Reorder the Z axis `Rec` instances.
   1140 
   1141 :Parameters:
   (...)
   1170 
   1171 """
   1172 indices_new = []
-> 1173 zpos = pmaxes.index(z_axis)
   1174 aaa0 = indices[0]
   1175 indices2 = [aaa0]

ValueError: 'domainaxis1' is not in list

This bug was introduced at v3.15.0, and is easily fixed. PR to follow.

>>> cf.environment(paths=False)
Platform: Linux-5.15.0-73-generic-x86_64-with-glibc2.35
HDF5 library: 1.12.2
netcdf library: 4.8.1
udunits2 library: miniconda3/lib/libudunits2.so.0
esmpy/ESMF: 8.2.0
Python: 3.10.10
dask: 2023.4.1
netCDF4: 1.6.2
psutil: 5.9.5
packaging: 23.0
numpy: 1.22.3
scipy: 1.10.1
matplotlib: 3.7.1
cftime: 1.6.2
cfunits: 3.3.6
cfplot: 3.2.12
cfdm: 1.10.1.0
cf: 3.15.1