Remove redundant and erroneous standard_name to LBFC/STASH PP save rules.

[bjlittle]

Working with AQUM revealed that loading a Fieldsfile with a PP-field of stash code 2 is translated to a cube with standard_name of eastward_wind, and that a PP-field of stash code 3 is translated to a cube with standard_name of northward_wind.

On saving such cubes, the PP save rules set/clobber the LBFC and LBUSER[3] (stash section and item) based only on the standard_name of the cube:

• For eastward_wind it forces 56 and 15201,
• For northward_wind it forces 57 and 15202.

These PP save rules are clearly wrong. It is not safe to translate from standard_name to stash code.

These save rules have been removed, along with several other such similar rules. All test still pass after removal, so thankfully we don't have current tests that rely on this erroneous behaviour.

[rhattersley]

I've spoken with @marqh and we've agreed that it be nice to keep the LBFC mappings. Would that still solve your problem?

[bjlittle]

Okay, that works for me.

I've checked the source AQUM FF and all PP-fields with a stash code of 2 have an LBFC = 56, and all PP-fields with a stash code of 3 have an LBFC = 57.

Excellent spot @rhattersley! Otherwise I would have lost the LBFC on saving. I'll resubmit the PR 😃

[rhattersley]

Do the tests, extests, doctests, etc. all pass already? (Oh, for a working Travis-CI config ;-))

[bjlittle]

Yes, yes and yes.

Although, there are (I assume) pre-existing failures on master for unittests and extests.

A fresh branch cut from upstream/master has a FAIL: test_simple (iris.tests.test_mapping.TestMappingSubRegion), and the extest failure FAIL: test_lagged_ensemble (example_tests.test_lagged_ensemble.TestLaggedEnsemble).

These are both image differences.

[rhattersley]

These are both image differences.

You have to be careful which version of Cartopy you run the tests against. And when I say "careful", I probably mean "lucky" as it's not exactly clear which version you should be using. (Oh, for a working Travis setup which would formally capture some of this! ;-))

I've run the tests myself and it's lookin' good, so I'm happy to merge.

[pelson]

Cartopy v0.4.0?