WIP: Revert to Python 3.7

[effigies]

Maybe the problem with #2409 is just nipype + Python 3.8+.

[mgxd]

I wonder if this is the same segfault

Traceback (most recent call last):
  File "/usr/local/miniconda/lib/python3.7/site-packages/nipype/pipeline/plugins/multiproc.py", line 67, in run_node
    result["result"] = node.run(updatehash=updatehash)
  File "/usr/local/miniconda/lib/python3.7/site-packages/nipype/pipeline/engine/nodes.py", line 516, in run
    result = self._run_interface(execute=True)
  File "/usr/local/miniconda/lib/python3.7/site-packages/nipype/pipeline/engine/nodes.py", line 635, in _run_interface
    return self._run_command(execute)
  File "/usr/local/miniconda/lib/python3.7/site-packages/nipype/pipeline/engine/nodes.py", line 741, in _run_command
    result = self._interface.run(cwd=outdir)
  File "/usr/local/miniconda/lib/python3.7/site-packages/nipype/interfaces/base/core.py", line 434, in run
    runtime = self._run_interface(runtime)
  File "/usr/local/miniconda/lib/python3.7/site-packages/nipype/interfaces/fsl/preprocess.py", line 164, in _run_interface
    self.raise_exception(runtime)
  File "/usr/local/miniconda/lib/python3.7/site-packages/nipype/interfaces/base/core.py", line 760, in raise_exception
    ).format(**runtime.dictcopy())
RuntimeError: Command:
bet /scratch/fmriprep_wf/single_subject_100185_wf/func_preproc_task_machinegame_run_02_wf/initial_boldref_wf/enhance_and_skullstrip_bold_wf/n4_correct/ref_sbref_corrected.nii.gz /scratch/fmriprep_wf/single_subject_100185_wf/func_preproc_task_machinegame_run_02_wf/initial_boldref_wf/enhance_and_skullstrip_bold_wf/skullstrip_first_pass/ref_sbref_corrected_brain.nii.gz -f 0.20 -m
Standard output:

Standard error:
Segmentation fault (core dumped)
Return code: 0

[effigies]

That would be a relief. Shall we revert FSL for now?

[mgxd]

i'd like to test locally first, but if it ends up being complicated i'm fine with downgrading.

[effigies]

Well, these are just experiments, so I'll see if that's the root of it. Won't merge anything.

[effigies]

Another option: Can we try FSL 6, if we're using neurodocker builds?

[mgxd]

this can be closed since #2409 is in