projection coordinates cannot pass the check

[charlienegri]

Version of compliance checker running: IOOS compliance checker version 5.1.2.dev1+g651b8c7

Describe the checker this affects:
CF 1.8

Describe the issue below:
In case projection coordinates with units in Cartesian system are present, like in the header pasted below, they get listed among other latitude/longitude coordinates by the get_latitude_variables() function in because of the axis: Y attribute, but then do not pass the units check. so they should either be excluded by the list (the function get_true_latitude_variables does that for example, but is not used anymore), or a special case should be made.

Attach a minimal CDL or NetCDF file which is able to reproduce the issue

variables:
	float nox_background_concentration(time, j, i) ;
		nox_background_concentration:_FillValue = -99.f ;
		nox_background_concentration:units = "ug/m3" ;
		nox_background_concentration:coordinates = "lon lat" ;
	int projection_lambert ;
		projection_lambert:grid_mapping_name = "lambert_conformal_conic" ;
		projection_lambert:standard_parallel = 63.3, 63.3 ;
		projection_lambert:longitude_of_central_meridian = 15. ;
		projection_lambert:latitude_of_projection_origin = 63.3 ;
		projection_lambert:earth_radius = 6371000. ;
	float i(i) ;
		i:_FillValue = 0.f ;
		i:standard_name = "projection_x_coordinate" ;
		i:long_name = "x-coordinate in Cartesian system" ;
		i:units = "m" ;
		i:axis = "X" ;
	float j(j) ;
		j:_FillValue = 0.f ;
		j:standard_name = "projection_y_coordinate" ;
		j:long_name = "y-coordinate in Cartesian system" ;
		j:units = "m" ;
		j:axis = "Y" ;
	float lat(j, i) ;
		lat:_FillValue = -999.f ;
		lat:long_name = "latitude" ;
		lat:units = "degrees_north" ;
		lat:standard_name = "latitude" ;
	float lon(j, i) ;
		lon:_FillValue = -999.f ;
		lon:standard_name = "longitude" ;
		lon:long_name = "longitude" ;
		lon:units = "degrees_east" ;
	int time(time) ;
		time:units = "seconds since 2022-01-01T00:00:00+00:00" ;
		time:calendar = "proleptic_gregorian" ;

[benjwadams]

CDL does not output netCDF with ncgen

[charlienegri]

test_slice.nc.gz