API: GH #2013 make regrid arguments, docstring consistent

[ellequelle]

Rationale

Addresses #2013

Implications

This is a change to the API for img_transform.regrid

I changed the name of the 4th argument from source_cs to source_proj to be consistent with other argument names. It's probably uncommon for source projection object to be passed as a keyword argument since it's the fourth of six positional arguments.

Old function signature:

cartopy/lib/cartopy/img_transform.py

Lines 222 to 223 in 22cdafc

	def regrid(array, source_x_coords, source_y_coords, source_cs, target_proj,
	target_x_points, target_y_points, mask_extrapolated=False):

New function signature:

def regrid(array, source_x_coords, source_y_coords, source_proj, target_proj,
           target_x_points, target_y_points, mask_extrapolated=False)

[greglucas]

👍 I think this has little chance of impacting people downstream and isn't worth doing a lot of deprecation dance around.

[dopplershift]

I agree, my only concern is the test failures, which I've not had a chance to dig into to see if they're related.

[ellequelle]

I've been confused by this one, but I get an identical error (cartopy.tests.test_shapereader.TestLakes) when testing the head branch on my computer, so it doesn't seem to be due to any of these changes.

[greglucas]

Yes, that looks like the same error as here: #2012
which is caused by pyshp, and our minimum dependencies is the only location where we are using pyshp.

[greglucas]

Thanks, @ellequelle!