antsIntroduction fails when -t RA is set

[lsqshr]

When I used nipype.interfaces.ants.legacy import antsIntroduction with setting XX.inputs.transformation_model='RA' (only Rigid+Affine registration), the registration failed by throwing a FileNotFoundError
'''
FileNotFoundError: File/Directory '/tmp/.../ants/ants_InverseWarp.nii.gz' not found for antsIntroduction output 'inverse_warp_field'.
'''
In commandline antsIntroduction ... runs without problem.

There are no displacement related outputs should be produced if no non-rigid registration is performed. Is it possible to make these outputs optional by default?

[satra]

@lsqshr - since this is in the legacy code for ants we haven't paid much attention to it.

you could make a change here:

https://github.com/nipy/nipype/blob/master/nipype/interfaces/ants/legacy.py#L69

but in the corresponding list outputs function you would have to check for transforms requested.

[lsqshr]

@satra Thanks for the response I will see what I could do

[lsqshr]

This little fix was done at #1009. Could it be merged? Though antsIntroduction is in the legacy code, it is pretty handy for general normalisation purposes.