TEST: Get string paths for test files

Closes gh-2513

Author: effigies

nipype/algorithms/tests/test_mesh_ops.py

@@ -21,7 +21,7 @@ def test_ident_distances(tmpdir):
     dist_ident = m.ComputeMeshWarp()
     dist_ident.inputs.surface1 = in_surf
     dist_ident.inputs.surface2 = in_surf
-    dist_ident.inputs.out_file = tmpdir.join('distance.npy')
+    dist_ident.inputs.out_file = tmpdir.join('distance.npy').strpath
     res = dist_ident.run()
     assert res.outputs.distance == 0.0
 
@@ -35,7 +35,7 @@ def test_trans_distances(tmpdir):
     from ...interfaces.vtkbase import tvtk
 
     in_surf = example_data('surf01.vtk')
-    warped_surf = tmpdir.join('warped.vtk')
+    warped_surf = tmpdir.join('warped.vtk').strpath
 
     inc = np.array([0.7, 0.3, -0.2])
 
@@ -51,7 +51,7 @@ def test_trans_distances(tmpdir):
     dist = m.ComputeMeshWarp()
     dist.inputs.surface1 = in_surf
     dist.inputs.surface2 = warped_surf
-    dist.inputs.out_file = tmpdir.join('distance.npy')
+    dist.inputs.out_file = tmpdir.join('distance.npy').strpath
     res = dist.run()
     assert np.allclose(res.outputs.distance, np.linalg.norm(inc), 4)
     dist.inputs.weighting = 'area'