Disallow print statements for debugging

[MarcoGorelli]

Description

Checklist

• Follows official PR format
• Includes a sample plot to visually illustrate the changes (only for plot-related functions)
• New features are properly documented (with an example if appropriate)?
• Includes new or updated tests to cover the new feature
• Code style correct (follows pylint and black guidelines)
• Changes are listed in changelog

Following up on @canyon289 's suggestion - this is to avoid problems like #1560

[canyon289]

Thanks for this contribution Marco.

One question related I think we should probably disable prints entirely and just use logging. A little outside of the scope of PR but thoughts?

For this PR scope I think this looks good

[OriolAbril]

One question related I think we should probably disable prints entirely and just use logging. A little outside of the scope of PR but thoughts?

I think we already use only logging and warnings for all our messages. IIUC, the two modified lines that add file=sys.stdout are the only print occurrences in the codebase, and they are two tests.

[ahartikainen]

Is this PR adding a check that there are no print statements in the codebase?

Why do we need to edit tests? They are hidden by default and when test fails, the printed parts are shown (also -s should show the prints when running locally)

Can we skip checking test folder?

[MarcoGorelli]

Sure, done (bit unwieldy without pre-commit, but -not -path works)

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(did I really accidentally open a PR from my main branch? oops 🤦 )

[codecov]

Codecov Report

Merging #1746 (a348c94) into main (ae83908) will decrease coverage by 4.04%.
The diff coverage is 100.00%.

❗ Current head a348c94 differs from pull request most recent head 090a19c. Consider uploading reports for the commit 090a19c to get more accurate results

@@            Coverage Diff             @@
##             main    #1746      +/-   ##
==========================================
- Coverage   90.87%   86.82%   -4.05%     
==========================================
  Files         109      109              
  Lines       11844    11844              
==========================================
- Hits        10763    10284     -479     
- Misses       1081     1560     +479     

Impacted Files	Coverage Δ
arviz/stats/stats.py	96.60% <ø> (ø)
arviz/data/inference_data.py	83.71% <100.00%> (ø)
arviz/data/io_pyro.py	96.24% <100.00%> (ø)
arviz/plots/backends/bokeh/loopitplot.py	95.29% <100.00%> (ø)
arviz/plots/backends/matplotlib/loopitplot.py	86.36% <100.00%> (ø)
arviz/data/io_pymc3_3x.py	18.18% <0.00%> (-72.06%)	⬇️
arviz/data/io_pystan.py	62.12% <0.00%> (-33.96%)	⬇️
arviz/data/io_cmdstanpy.py	70.68% <0.00%> (-24.76%)	⬇️
arviz/data/io_emcee.py	93.38% <0.00%> (-4.96%)	⬇️
arviz/utils.py	88.81% <0.00%> (-0.33%)	⬇️

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