NOTE: since Travis relies on installing Iris from conda, this PR will not pass testing until the move of equalise_attributes to iris.util is within an Iris version that is available on conda. Merging will need to wait until then.

Depending on release timings, it may be necessary to extract the fix for test_grib1_hybrid_height into a patch for Iris-GRIB, since after the Iris-GRIB v0.15 release the climatological feature was released within Iris v2.3, breaking test_grib1_hybrid_height.

@trexfeathers Okay, I'd say pop pep8 into the environment.yml for now.

Ultimately, we'll move iris-grib to be black compliant akin to iris, but until then it makes sense to explicitly add pep8 as a testing dependency.

When we do move to black then we can remove the pep8 dependency and the associated test that need it.

Sound like a reasonable plan?

Note that, the iris-grib test will start working from iris 2.4.* onwards.

Awesome, thanks @trexfeathers 👍