update pyobject method for more recent pytave, add doctest

inst/@sym/pyobject.m

@@ -1,4 +1,4 @@
-%% Copyright (C) 2016 Colin B. Macdonald
+%% Copyright (C) 2016-2017 Colin B. Macdonald
 %%
 %% This file is part of OctSymPy.
 %%
@@ -24,10 +24,11 @@
 %% Example:
 %% @example
 %% @group
+%% @c doctest +SKIP_IF(~strcmp(sympref('ipc'), 'native')))
 %% syms x
 %% f = 2*sin(x/2);
 %% pyobject(f)
-%%   @result{} ans = [pyobject ...]
+%%   @result{} ans = [Python object of type sympy.core.mul.Mul]
 %%
 %%       2*sin(x/2)
 %%
@@ -39,7 +40,7 @@
 
 function y = pyobject (x)
 
-  y = py.sympy.S (char (x));
+  y = py.sympy.S (sympy (x));
 
   % Above is nice because it needs no imports.  But downside is some
   % things like NonElementaryIntegral and MatrixElement will fail.  See