raise exception from parent exception

[ahartikainen]

Submission Checklist

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

Summary

Raise child exception using from exc syntax.

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):

Ari Hartikainen

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 #284 into develop will not change coverage.
The diff coverage is 87.50%.

@@           Coverage Diff            @@
##           develop     #284   +/-   ##
========================================
  Coverage    76.07%   76.07%           
========================================
  Files            9        9           
  Lines         2194     2194           
========================================
  Hits          1669     1669           
  Misses         525      525           

Impacted Files	Coverage Δ
cmdstanpy/utils.py	77.37% <66.66%> (ø)
cmdstanpy/cmdstan_args.py	90.78% <100.00%> (ø)
cmdstanpy/model.py	81.69% <100.00%> (ø)
cmdstanpy/stanfit.py	95.56% <100.00%> (ø)

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[mitzimorris]

LGTM - many thanks!