Translate warnings to Python

[ischoegl]

Changes proposed in this pull request

• Translate warnings raised in C++ to Python warnings: warn_deprecated is raised as DeprecationWarning and warn_user is raised as UserWarning (on C++ the output is changed from CanteraWarning to UserWarning for consistency)
• Update year in License

If applicable, fill in the issue number this pull request is fixing

Closes Cantera/enhancements#136

If applicable, provide an example illustrating new features this pull request is introducing

>>> import cantera as ct
>>> gas = ct.Solution("h2o2.cti")
<stdin>:1: DeprecationWarning: XML_Node::build: 
The CTI and XML input file formats are deprecated and will be removed in
Cantera 3.0. Use 'cti2yaml.py' or 'ctml2yaml.py' to convert CTI or XML input
files to the YAML format. See https://cantera.org/tutorials/legacy2yaml.html
for more information.

and

>>> import warnings
>>> import cantera as ct
>>> with warnings.catch_warnings():
...     warnings.simplefilter("ignore")
...     gas = ct.Solution("gri30.cti")
... 
>>> gas
<cantera.composite.Solution object at 0x7f630d950dc0>

Another nice thing is that users will be pointed to the line in existing Python code where the warning is invoked, e.g.

In [1]: %run custom_reactions.py
/work/GitHub/cantera/interfaces/cython/cantera/examples/kinetics/custom_reactions.py:34: DeprecationWarning: XML_Node::build: 
The CTI and XML input file formats are deprecated and will be removed in
Cantera 3.0. Use 'cti2yaml.py' or 'ctml2yaml.py' to convert CTI or XML input
files to the YAML format. See https://cantera.org/tutorials/legacy2yaml.html
for more information.

(this is from an instance where a DeprecationWarning in an example was previously not caught by the test suite; this is also addressed in this PR)

Checklist

• The pull request includes a clear description of this code change
• Commit messages have short titles and reference relevant issues
• Build passes (scons build & scons test) and unit tests address code coverage
• Style & formatting of contributed code follows contributing guidelines
• The pull request is ready for review

[codecov]

Codecov Report

Merging #1201 (4a6c372) into main (0dba120) will decrease coverage by 0.02%.
The diff coverage is 76.92%.

@@            Coverage Diff             @@
##             main    #1201      +/-   ##
==========================================
- Coverage   65.41%   65.38%   -0.03%     
==========================================
  Files         318      318              
  Lines       46085    46095      +10     
  Branches    19604    19604              
==========================================
- Hits        30145    30141       -4     
- Misses      13426    13439      +13     
- Partials     2514     2515       +1     

Impacted Files	Coverage Δ
include/cantera/cython/wrappers.h	85.15% <50.00%> (-0.33%)	⬇️
include/cantera/base/global.h	81.81% <60.00%> (-2.40%)	⬇️
src/base/application.cpp	63.98% <83.33%> (-1.26%)	⬇️
include/cantera/base/logger.h	78.57% <100.00%> (+5.84%)	⬆️
src/base/application.h	69.76% <100.00%> (-15.95%)	⬇️
src/base/global.cpp	70.58% <100.00%> (-4.26%)	⬇️
src/kinetics/Reaction.cpp	81.07% <0.00%> (+0.17%)	⬆️
... and 1 more

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[bryanwweber]

Thanks @ischoegl! This looks like it will be a nice change, and it'll be nice to be able to manage warnings by built-in Python methods.

[ischoegl]

@bryanwweber ... thank you for the review!

I ended up implementing a more comprehensive C++ backend for a more fine-grained warning system that should mesh well with various API's. I also included a test that ensures that warnings are raised correctly.

[bryanwweber]

Thanks @ischoegl! A couple more small things here.

[ischoegl]

@bryanwweber ... 😅 Testing the warning system ended up creating battles with some of the work-arounds that were put in since 2.5.1 for testing purposes, specifically 5f5a005 and 80c1e56. As those methods do not allow for fine-grained control and are de-facto redundant, I decided to take them out.

Regarding your comment about pytest: using warning filters would allow for further removing methods that @speth put in earlier, specifically ct.make_deprecation_warnings_fatal() and ct.suppress_deprecation_warnings(). Removing those would be a lot more intrusive and should probably be handled in a different PR (if at all) ...

[speth]

Thanks, @ischoegl. Overall, I think this is a good change, and most of the implementation makes sense to me. There were just a few particular issues that I wanted to address.

[ischoegl]

@bryanwweber and @speth ... I believe both of your change requests are now fully addressed. Thanks for all suggestions!

[bryanwweber]

This passes for me if I run pytest directly, but not running pytest via scons test-python. Will revert those changes if I can't find a quick fix 😢

[ischoegl]

@bryanwweber ... thanks for trying to simplify by introducing pytest.fixtures. While I agree that it's worthwhile testing this approach, it may be best to drop it from this PR. It's a tangent here and it can be easily tested in a dedicated PR?

[bryanwweber]

@ischoegl I've got it working locally, I just need to commit & push

[bryanwweber]

@ischoegl Presuming the checks pass this time, this should be good to

[ischoegl]

@bryanwweber ... 🎉 ... things passed. Looks like the fixture is pretty similar to what unittest did, which is good news! So thank you for looking into this! Beyond, I think all that's left is your approval 😉 ...

[bryanwweber]

@ischoegl Great minds!!! Merged 😄