Fixed leaf_nodes computation

[lucianopaz]

This fixes #3643. I have to run now but I'll add a test, some release notes and refactor a bit of old dangling code by tomorrow. After that, it should be ok to merge.

[lucianopaz]

This should be ready for merge now. I don't know what's happening with coveralls

[lucianopaz]

Rebased on top of master to get coveralls parallel reports working. Hopefully, the coverage should be fixed now.

[rpgoldman]

Only minor stylistic changes. It looks ready to go.

[lucianopaz]

Thanks @rpgoldman for the careful review! I'll change what you suggested tomorrow

[rpgoldman]

Thanks @rpgoldman for the careful review! I'll change what you suggested tomorrow

You're very welcome! Thanks for doing this! It will make things much more testable, which is very good!

[codecov]

Codecov Report

Merging #3645 into master will increase coverage by 0.9%.
The diff coverage is 92.44%.

@@            Coverage Diff            @@
##           master    #3645     +/-   ##
=========================================
+ Coverage    89.8%   90.71%   +0.9%     
=========================================
  Files         134      133      -1     
  Lines       20065    20386    +321     
=========================================
+ Hits        18020    18493    +473     
+ Misses       2045     1893    -152

Impacted Files	Coverage Δ
pymc3/distributions/__init__.py	100% <ø> (ø)	⬆️
pymc3/distributions/distribution.py	94.73% <ø> (-0.39%)	⬇️
pymc3/data.py	79.76% <ø> (+0.11%)	⬆️
pymc3/ode/utils.py	100% <100%> (ø)	⬆️
pymc3/tests/test_missing.py	100% <100%> (ø)	⬆️
pymc3/tests/test_modelcontext.py	100% <100%> (ø)	⬆️
pymc3/tests/test_data_container.py	100% <100%> (ø)	⬆️
pymc3/tests/test_distributions_random.py	99.13% <100%> (-0.14%)	⬇️
pymc3/exceptions.py	100% <100%> (ø)	⬆️
pymc3/tests/test_model.py	100% <100%> (ø)	⬆️
... and 144 more

[lucianopaz]

@rpgoldman, I went through the suggestions you made and now this PR should be ready for review.

[lucianopaz]

It looks like the failing test was purely travis CI's fault

[junpenglao]

Is this ready to merge @lucianopaz ?

[lucianopaz]

@junpenglao, yes, it should be ready to merge. I can change the minor nitpick tomorrow if no one is in a rush to merge this

[junpenglao]

Awesome! Great work as always ;-)