Support PyStan3

.pylintrc

@@ -249,6 +249,7 @@ good-names=i,
            mu,
            tr,
            ex,
+	   eta,
            Run,
            _,
            _log

.travis.yml

@@ -10,6 +10,9 @@ matrix:
   - name: "Python 3.6 Unit Test"
     python: 3.6
     env: PYSTAN_VERSION=latest NAME="UNIT"
+  - name: "Python 3.6 Unit Test - PyStan preview"
+    python: 3.6
+    env: PYSTAN_VERSION=preview NAME="UNIT"
   - name: "Python 3.5 Unit Test"
     python: 3.5
     env: PYSTAN_VERSION=latest NAME="UNIT"

arviz/data/converters.py

@@ -53,6 +53,8 @@ def convert_to_inference_data(obj, *, group="posterior", coords=None, dims=None,
         return InferenceData.from_netcdf(obj)
     elif obj.__class__.__name__ == "StanFit4Model":  # ugly, but doesn't make PyStan a requirement
         return from_pystan(posterior=obj, coords=coords, dims=dims, **kwargs)
+    elif obj.__class__.__module__ == "stan.fit":  # ugly, but doesn't make PyStan3 a requirement
+        return from_pystan(posterior=obj, coords=coords, dims=dims, **kwargs)
     elif obj.__class__.__name__ == "MultiTrace":  # ugly, but doesn't make PyMC3 a requirement
         return from_pymc3(trace=obj, coords=coords, dims=dims, **kwargs)
     elif obj.__class__.__name__ == "EnsembleSampler":  # ugly, but doesn't make emcee a requirement