adding exists=True for subjects_dir in FSSourceInputSpec

Author: djarecka

nipype/interfaces/io.py

@@ -1485,7 +1485,7 @@ def _list_outputs(self):
 
 
 class FSSourceInputSpec(BaseInterfaceInputSpec):
-    subjects_dir = Directory(mandatory=True,
+    subjects_dir = Directory(exists=True, mandatory=True,
                              desc='Freesurfer subjects directory.')
     subject_id = Str(mandatory=True,
                      desc='Subject name for whom to retrieve data')

nipype/interfaces/tests/test_io.py

@@ -407,6 +407,13 @@ def test_freesurfersource():
     assert fss.inputs.subjects_dir == Undefined
 
 
+def test_freesurfersource_incorrectdir():
+    fss = nio.FreeSurferSource()
+    with pytest.raises(Exception) as err:
+        fss.inputs.subjects_dir = 'path/to/no/existing/directory'
+    assert "TraitError" == err.typename
+
+
 def test_jsonsink_input():
 
     ds = nio.JSONFileSink()