Patch 5561 - Standardized return codes for gdal-utils

[maphew]

What does this PR do?

Standardized return codes for gdal-utils scripts when called without arguments

What are related issues/pull requests?

• Standardize gdal-utils scripts return codes Standardize gdal-utils scripts return codes #5561
• Mailing list: [gdal-dev] Standardize gdal-utils scripts return code for "no arguments"
• Branch patch-5561, standardized to return 2
• Branch patch-5561-ret2, standardized to return 2 merged into patch-5561.

Tasklist

• Change return codes to 2 that were
  • -1
  • 0 auxillary Skip, these are not meant to be scripts.
  • - 1
  • 2 scripts that use GDALArgumentParser (ref)
• Add test case(s)
• Add documentation
• Review
• Adjust for comments
• All CI builds and checks have passed

Environment

Provide environment details, if relevant:

• Python 3

Updated 2022-05-23

[rcoup]

Is there a reason we can't standardise on 2 everywhere?

ie:
1 = general error
2 = you provided some bad arguments / no arguments — this should have been expected
other numbers = specific error

[maphew]

Define 'everywhere' :) If you're talking about gdal_translate and friends, yes I think that's a good idea, but is beyond the scope of this PR (and more importantly my skills!) It is my motivation to standardize return codes and other related things in the python scripts portion of gdal.

[maphew]

Wow, what a long haul this 'simple' idea turned into! But, I think it's finally ready. Please have a look @rouault, @idanmiara.

fft.py fails flake8 test because of import *. I'm unfamiliar with fourier transform module(s) and don't know what the correct remedy is here.

[rouault]

fft.py fails flake8 test because of import *

I don't understand what you mean. I only see a "import FFT" in that file

[maphew]

fft.py fails flake8 test because of import *

I don't understand what you mean. I only see a "import FFT" in that file

try:
    import FFT
except ModuleNotFoundError:
    from numpy.fft import *

Oh! Git blame says I'm the one who added it, in 04aad75, to work around an import error. I don't remember what made me think that was a good alternative. I've changed it to gracefully exit if FFT module not found. It's might be better to use numpy.fft instead, but it doesn't have function 'fft2d' and I don't know what the best equivalent function is.