Merge pull request dipy#1243 from ghoshbishakh/betterErrors

Better fvtk.viz error when no VTK installed

dipy/utils/tests/test_tripwire.py

@@ -20,6 +20,8 @@ def test_tripwire():
                   getattr,
                   silly_module_name,
                   'do_silly_thing')
+    assert_raises(TripWireError,
+                  silly_module_name)
     # Check AttributeError can be checked too
     try:
         silly_module_name.__wrapped__

dipy/utils/tripwire.py

@@ -41,9 +41,14 @@ class TripWire(object):
         ...
     TripWireError: We do not have silly_module_name
     """
+
     def __init__(self, msg):
         self._msg = msg
 
     def __getattr__(self, attr_name):
         ''' Raise informative error accessing attributes '''
         raise TripWireError(self._msg)
+
+    def __call__(self, *args, **kwargs):
+        ''' Raise informative error while calling '''
+        raise TripWireError(self._msg)

dipy/viz/fvtk.py

@@ -79,6 +79,9 @@
     msg = "Python VTK is not installed"
     warn(msg)
 
+    ren, have_ren, _ = optional_package('dipy.viz.window.ren',
+                                        'Python VTK is not installed')
+
 
 def dots(points, color=(1, 0, 0), opacity=1, dot_size=5):
     """ Create one or more 3d points