[FIX] Removed exists=True from MathsOutput

[0nu]

Summary

When setting MathsCommand().inputs.out_file argument, a Trait error is thrown because of the exists=True, although this file is to be created. This PR fixed this by removing the exists=True argument.

Fixes #3384 .

List of changes proposed in this PR (pull-request)

• Removed exists=True from MathsOutput File().

Acknowledgment

• (Mandatory) I acknowledge that this contribution will be available under the Apache 2 license.

[effigies]

I think you're going to need to rerun make check-before-commit. (See https://github.com/nipy/nipype/blob/master/CONTRIBUTING.md#making-a-change)

[codecov]

Codecov Report

Merging #3385 (4362809) into master (6a7837c) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #3385   +/-   ##
=======================================
  Coverage   65.13%   65.13%           
=======================================
  Files         307      307           
  Lines       40372    40372           
  Branches     5336     5336           
=======================================
  Hits        26297    26297           
  Misses      13003    13003           
  Partials     1072     1072           

Flag	Coverage Δ
unittests	64.87% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
nipype/interfaces/fsl/maths.py	98.25% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6a7837c...4362809. Read the comment docs.

[effigies]

Ah, nevermind. It seems that exists=True isn't a thing we check for in specs, so no changes would result. Thanks!

[0nu]

Thanks!