Feature/22 better error handling

[mitzimorris]

Submission Checklist

• Run unit tests
• Declare copyright holder and open-source license: see below

Summary

When CmdStan method returns a non-zero error code, return as much useful information as can be scraped out of the stdout and stderr messages, plus information about the run and locations of resulting output files, if any.

Exposed and expanded RunSet method get_err_msgs; this function was written a long time ago, but wasn't being called by the CmdStanModel methods. It attempts to get just the relevant messages from the information spew that's written to stdout, in addtion to all msgs written to stderr. It seems to do an OK job on the most common and annoying problem - return code 70 which happens when there's a mismatch between the model's data block variable declarations and the input data.

Copyright and Licensing

Please list the copyright holder for the work you are submitting (this will be you or your assignee, such as a university or company): Columbia University

By submitting this pull request, the copyright holder is agreeing to license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)

[codecov-commenter]

Codecov Report

Merging #280 into develop will increase coverage by 0.13%.
The diff coverage is 81.81%.

@@             Coverage Diff             @@
##           develop     #280      +/-   ##
===========================================
+ Coverage    75.89%   76.03%   +0.13%     
===========================================
  Files            9        9              
  Lines         2199     2195       -4     
===========================================
  Hits          1669     1669              
+ Misses         530      526       -4     

Impacted Files	Coverage Δ
cmdstanpy/model.py	81.69% <57.14%> (+0.71%)	⬆️
cmdstanpy/stanfit.py	95.37% <93.33%> (-0.12%)	⬇️

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[ahartikainen]

LGTM

[ahartikainen]

This is not needed anymore?

[mitzimorris]

right - at the stan::services layer, https://github.com/stan-dev/stan/tree/develop/src/stan/services/optimize - if you look at these methods, they don't take a diagnostics file as an argument.