diff --git a/nipype/interfaces/afni/utils.py b/nipype/interfaces/afni/utils.py
index e20fe1d5f..88a317b8c 100644
--- a/nipype/interfaces/afni/utils.py
+++ b/nipype/interfaces/afni/utils.py
@@ -602,12 +602,12 @@ class CatMatvecInputSpec(AFNICommandInputSpec):
                "This feature could be used, with clever scripting, to input"
                "a matrix directly on the command line to program 3dWarp.",
         argstr="-MATRIX",
-        xor=['oneline','fourXfour'])
+        xor=['oneline', 'fourxfour'])
     oneline = traits.Bool(
         descr="indicates that the resulting matrix"
               "will simply be written as 12 numbers on one line.",
         argstr="-ONELINE",
-        xor=['matrix','fourXfour'])
+        xor=['matrix', 'fourxfour'])
     fourxfour = traits.Bool(
         descr="Output matrix in augmented form (last row is 0 0 0 1)"
               "This option does not work with -MATRIX or -ONELINE",

typo in trait name of AFNI CatMatvec interface
### Summary
typo in `afni.Catmatvec`: trait name is `fourxfour` not `fourXfour`
https://github.com/nipy/nipype/blob/master/nipype/interfaces/afni/utils.py#L610

### Actual behavior
```Python
from nipype.interfaces import afni

cat_matvec = afni.CatMatvec()
cat_matvec.inputs.oneline = True
```
throws 
```Python
AttributeError: 'CatMatvecInputSpec' object has no attribute 'fourXfour'
```

### Platform details:

Please paste the output of: `python -c "import nipype; print(nipype.get_info()); print(nipype.__version__)"`

{'nibabel_version': '2.1.0', 'sys_executable': '/home/salma/anaconda2/bin/python', 'networkx_version': '1.11', 'numpy_version': '1.13.1', 'sys_platform': 'linux2', 'sys_version': '2.7.13 |Anaconda custom (64-bit)| (default, Dec 20 2016, 23:09:15) \n[GCC 4.4.7 20120313 (Red Hat 4.4.7-1)]', 'commit_source': u'repository', 'commit_hash': '7ead69d', 'pkg_path': 'nipype', 'nipype_version': u'1.0.0-dev+g7ead69d', 'traits_version': '4.6.0', 'scipy_version': '0.19.1'}
1.0.0-dev+g7ead69d

diff --git a/nipype/interfaces/afni/tests/test_auto_CatMatvec.py b/nipype/interfaces/afni/tests/test_auto_CatMatvec.py
index 4b79cd91d..d3d94569b 100644
--- a/nipype/interfaces/afni/tests/test_auto_CatMatvec.py
+++ b/nipype/interfaces/afni/tests/test_auto_CatMatvec.py
@@ -23,11 +23,11 @@ def test_CatMatvec_inputs():
     ),
     matrix=dict(argstr='-MATRIX',
     descr="indicates that the resulting matrix willbe written to outfile in the 'MATRIX(...)' format (FORM 3).This feature could be used, with clever scripting, to inputa matrix directly on the command line to program 3dWarp.",
-    xor=['oneline', 'fourXfour'],
+    xor=['oneline', 'fourxfour'],
     ),
     oneline=dict(argstr='-ONELINE',
     descr='indicates that the resulting matrixwill simply be written as 12 numbers on one line.',
-    xor=['matrix', 'fourXfour'],
+    xor=['matrix', 'fourxfour'],
     ),
     out_file=dict(argstr=' > %s',
     descr='File to write concattenated matvecs to',

pip install -e .[dev]
parse_log_pytest
requirements.txt
pytest
apt-get update apt-get install -y gcc
3.6
requirements.txt
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
attrs==22.2.0
certifi==2021.5.30
click==8.0.4
configparser==5.2.0
decorator==4.4.2
funcsigs==1.0.2
future==1.0.0
importlib-metadata==4.8.3
iniconfig==1.1.1
isodate==0.6.1
lxml==5.3.1
mock==5.2.0
networkx==2.5.1
nibabel==3.2.2
-e git+https://github.com/nipy/nipype.git@7ead69d1aeb24f0d0884efe03075ef7de1759e1c#egg=nipype
numpy==1.19.5
packaging==21.3
pluggy==1.0.0
prov==1.5.0
py==1.11.0
pydotplus==2.0.2
pyparsing==3.1.4
pytest==7.0.1
python-dateutil==2.9.0.post0
rdflib==5.0.0
scipy==1.5.4
simplejson==3.20.1
six==1.17.0
tomli==1.2.3
traits==6.4.1
typing_extensions==4.1.1
zipp==3.6.0

name: nipype
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - pip=21.2.2=py36h06a4308_0
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - attrs==22.2.0
      - click==8.0.4
      - configparser==5.2.0
      - decorator==4.4.2
      - funcsigs==1.0.2
      - future==1.0.0
      - importlib-metadata==4.8.3
      - iniconfig==1.1.1
      - isodate==0.6.1
      - lxml==5.3.1
      - mock==5.2.0
      - networkx==2.5.1
      - nibabel==3.2.2
      - numpy==1.19.5
      - packaging==21.3
      - pluggy==1.0.0
      - prov==1.5.0
      - py==1.11.0
      - pydotplus==2.0.2
      - pyparsing==3.1.4
      - pytest==7.0.1
      - python-dateutil==2.9.0.post0
      - rdflib==5.0.0
      - scipy==1.5.4
      - simplejson==3.20.1
      - six==1.17.0
      - tomli==1.2.3
      - traits==6.4.1
      - typing-extensions==4.1.1
      - zipp==3.6.0
prefix: /opt/conda/envs/nipype

nipype/interfaces/afni/tests/test_auto_CatMatvec.py::test_CatMatvec_inputs
nipype/interfaces/afni/tests/test_auto_CatMatvec.py::test_CatMatvec_outputs
nipype/interfaces/afni/utils.py
nipype/interfaces/afni/utils.py