Fix calculating area slices for flipped projections

[pnuu]

This fixes a segmentation fault for Satpy data reduction when the source area is flipped and GEO data has space surrounding the full disk data. In this case pykdtree was passed coordinates that were inf which causes segmentation fault.

• Closes segmentation fault or AssertionError when resampling #274
• Tests added
• Tests passed
• Passes git diff origin/master **/*py | flake8 --diff

[coveralls]

Coverage increased (+0.0002%) to 91.947% when pulling a20b247 on pnuu:debug-kdtree-segfault into b7c769b on pytroll:master.

[codecov]

Codecov Report

Merging #277 into master will increase coverage by 0.89%.
The diff coverage is 95.00%.

@@            Coverage Diff             @@
##           master     #277      +/-   ##
==========================================
+ Coverage   91.94%   92.83%   +0.89%     
==========================================
  Files          42       42              
  Lines        8183     9427    +1244     
==========================================
+ Hits         7524     8752    +1228     
- Misses        659      675      +16     

Impacted Files	Coverage Δ
pyresample/geometry.py	86.12% <93.33%> (+3.56%)	⬆️
pyresample/test/test_geometry.py	98.64% <100.00%> (+0.89%)	⬆️
pyresample/test/test_kd_tree.py	97.01% <100.00%> (-0.27%)	⬇️
pyresample/bucket/__init__.py	98.59% <0.00%> (-0.33%)	⬇️
pyresample/test/utils.py	71.07% <0.00%> (-0.21%)	⬇️
pyresample/test/test_grid.py	100.00% <0.00%> (ø)
pyresample/test/test_bucket.py	100.00% <0.00%> (ø)
pyresample/test/test_utils.py	97.89% <0.00%> (+0.51%)	⬆️
... and 4 more

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[gerritholl]

I tested this with my example and I no longer get a segmentation fault. It successfully generates this image:

Using:

from satpy import Scene
from satpy.utils import debug_on
debug_on()
from glob import glob
sc = Scene(glob("/media/nas/x21308/2020_04_MTG_unofficial_Testdata/20130804_RC72/W_XX-EUMETSAT-Darmstadt,IMG+SAT,MTI1+FCI-1C-RRAD-FDHSI-FD--CHK-BODY--L2P-NC4E_C_EU*.nc"), reader="fci_l1c_fdhsi")
sc.load(["ir_123"])
nsc = sc.resample("fci_0deg_2km")
nsc["ir_123"].compute()
nsc.save_dataset("ir_123", "/tmp/ir_123.png")

[djhoese]

What happened here?

[djhoese]

Oh this is my change from #265

[mraspaud]

LGTM