Small fix to pydotprint_variables

theano/printing.py

@@ -992,7 +992,7 @@ def pydotprint_variables(vars,
         if nd.owner:
             plot_apply(nd.owner, depth)
     try:
-        g.write_png(outfile, prog='dot')
+        g.write(outfile, prog='dot', format=format)
     except pd.InvocationException, e:
         # Some version of pydot are bugged/don't work correctly with
         # empty label. Provide a better user error message.
@@ -1006,6 +1006,7 @@ def pydotprint_variables(vars,
                             " Theano. Using another version of pydot could"
                             " fix this problem. The pydot error is: " +
                             e.message)
+        raise
 
     print 'The output file is available at', outfile
 

theano/tests/test_printing.py

@@ -11,6 +11,7 @@ import theano.tensor as tensor
 from theano.printing import min_informative_str, debugprint
 from theano.compat.six import StringIO
 
+
 def test_pydotprint_cond_highlight():
     """
     This is a REALLY PARTIAL TEST.
@@ -44,6 +45,37 @@ def test_pydotprint_cond_highlight():
             ' is no IfElse node in the graph\n')
 
 
+def test_pydotprint_variables():
+    """
+    This is a REALLY PARTIAL TEST.
+
+    I did them to help debug stuff.
+
+    It make sure the code run.
+    """
+
+    # Skip test if pydot is not available.
+    if not theano.printing.pydot_imported:
+        raise SkipTest('pydot not available')
+
+    x = tensor.dvector()
+
+    s = StringIO()
+    new_handler = logging.StreamHandler(s)
+    new_handler.setLevel(logging.DEBUG)
+    orig_handler = theano.logging_default_handler
+
+    theano.theano_logger.removeHandler(orig_handler)
+    theano.theano_logger.addHandler(new_handler)
+    theano.theano_logger.removeHandler(orig_handler)
+    theano.theano_logger.addHandler(new_handler)
+    try:
+        theano.printing.pydotprint_variables(x * 2)
+    finally:
+        theano.theano_logger.addHandler(orig_handler)
+        theano.theano_logger.removeHandler(new_handler)
+
+
 def test_pydotprint_long_name():
     """This is a REALLY PARTIAL TEST.