No module named externals

[bamal]

I am using the nipype 0.12 package and I got this error

170516-16:10:38,459 workflow ERROR:
	 ['Node preproc.a0 failed to run on host mint.']
170516-16:10:38,459 workflow INFO:
	 Saving crash info to /home/boukhdha/neuropype_workshop/source_code/crash-20170516-161038-boukhdha-preproc.a0-7a2fc572-24a0-4f34-a8fa-c3b9e6b2c35b.pklz
170516-16:10:38,459 workflow INFO:
	 Traceback (most recent call last):
  File "/usr/local/lib/python2.7/dist-packages/nipype/pipeline/plugins/linear.py", line 39, in run
    node.run(updatehash=updatehash)
  File "/usr/local/lib/python2.7/dist-packages/nipype/pipeline/engine/nodes.py", line 394, in run
    self._run_interface()
  File "/usr/local/lib/python2.7/dist-packages/nipype/pipeline/engine/nodes.py", line 504, in _run_interface
    self._result = self._run_command(execute)
  File "/usr/local/lib/python2.7/dist-packages/nipype/pipeline/engine/nodes.py", line 630, in _run_command
    result = self._interface.run()
  File "/usr/local/lib/python2.7/dist-packages/nipype/interfaces/base.py", line 1034, in run
    runtime = self._run_wrapper(runtime)
  File "/usr/local/lib/python2.7/dist-packages/nipype/interfaces/base.py", line 991, in _run_wrapper
    runtime = self._run_interface(runtime)
  File "/usr/local/lib/python2.7/dist-packages/nipype/interfaces/utility.py", line 496, in _run_interface
    raise out
ImportError: No module named externals
Interface Function failed to run.