Uniformize UTF-8 naming

[BoboTiG]

Replace utf8 -> utf-8 everywhere.
It should have no impact, utf8 is an alias of utf-8 [1].

[1] https://github.com/python/cpython/blob/ee03bad25e83b00ba5fc2a0265b48c6286e6b3f7/Lib/encodings/aliases.py#L534

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Full story: I kind of need such uniformization for #1110 where I am adding tests. And I have to deal with our naming (utf8) and the one from requests or charset_normalizer (utf-8).
Note that this is a one-time small clean-up, and I can live without that patch being merged.

[codecov-commenter]

Codecov Report

Merging #1115 (f0ccf9f) into master (04d05a8) will increase coverage by 0.49%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1115      +/-   ##
==========================================
+ Coverage   96.35%   96.84%   +0.49%     
==========================================
  Files          64       65       +1     
  Lines        4137     4180      +43     
==========================================
+ Hits         3986     4048      +62     
+ Misses        151      132      -19     

Impacted Files	Coverage Δ
httpie/cli/requestitems.py	91.17% <ø> (ø)
tests/test_cli.py	100.00% <ø> (ø)
tests/test_downloads.py	100.00% <ø> (ø)
httpie/cli/argparser.py	96.35% <100.00%> (ø)
httpie/client.py	100.00% <100.00%> (ø)
httpie/config.py	90.00% <100.00%> (+0.12%)	⬆️
httpie/constants.py	100.00% <100.00%> (ø)
httpie/context.py	87.17% <100.00%> (+0.16%)	⬆️
httpie/models.py	92.00% <100.00%> (+0.10%)	⬆️
httpie/output/streams.py	99.03% <100.00%> (+8.74%)	⬆️
... and 19 more

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[BoboTiG]

It is finally not needed for #1110 but I am still for such clean-up, if you are OK with that @jakubroztocil :)

[jkbrzt]

We can remove the argument from .encode('utf-8') and .decode('utf-8') since it’s the default.

I’d also introduce a UTF8 = 'UTF-8' constant and use it instead of the string to avoid inconsistencies and to have a central place where we can talk about the encoding.

[BoboTiG]

Actually I did the exact opposite :)

I think it is a good thing to explicitly set the encoding everywhere to prevent surprises. And the PEP-597 will eventually throw warnings in a near future.

[BoboTiG]

/packit copr-build

[BoboTiG]

/packit copr-build

[jkbrzt]

Actually I did the exact opposite :)

I think it is a good thing to explicitly set the encoding everywhere to prevent surprises. And the PEP-597 will eventually throw warnings in a near future.

I believe the PEP only talks about open()’s encoding. For encode()/decode(), utf-8 is the argument’s default value:

str.encode(encoding="utf-8", errors="strict")
bytes.decode(encoding="utf-8", errors="strict")¶

https://docs.python.org/3/library/stdtypes.html#str.encode
https://docs.python.org/3/library/stdtypes.html#bytes.decode

[BoboTiG]

Oh how did miss that?!

I'll remove all encoding occurrences for those functions then 👍