distribution on new line in GraphViz node (#3957)

* distribution on new line in GraphViz node

* updating tests to check newline instead of space in graphviz graphs

Author: Spaak

pymc3/model_graph.py

@@ -147,7 +147,7 @@ def _make_node(self, var_name, graph):
             attrs['shape'] = 'box'
 
         graph.node(var_name.replace(':', '&'),
-                '{var_name} ~ {distribution}'.format(var_name=var_name, distribution=distribution),
+                '{var_name}\n~\n{distribution}'.format(var_name=var_name, distribution=distribution),
                 **attrs)
 
     def get_plates(self):

pymc3/tests/test_data_container.py

@@ -188,12 +188,12 @@ def test_model_to_graphviz_for_model_with_data_container(self):
         g = pm.model_to_graphviz(model)
 
         # Data node rendered correctly?
-        text = 'x [label="x ~ Data" shape=box style="rounded, filled"]'
+        text = 'x [label="x\n~\nData" shape=box style="rounded, filled"]'
         assert text in g.source
         # Didn't break ordinary variables?
-        text = 'beta [label="beta ~ Normal"]'
+        text = 'beta [label="beta\n~\nNormal"]'
         assert text in g.source
-        text = 'obs [label="obs ~ Normal" style=filled]'
+        text = 'obs [label="obs\n~\nNormal" style=filled]'
         assert text in g.source
 
     def test_explicit_coords(self):