eko fails to load an eko.tar

[niclaurenti]

The error I'm getting is the following

Traceback (most recent call last):
  File "/home/niccololaurenti/miniconda3/envs/nnpdf-dev/lib/python3.10/site-packages/eko/io/struct.py", line 853, in load
    with tarfile.open(tarpath) as tar:
  File "/home/niccololaurenti/miniconda3/envs/nnpdf-dev/lib/python3.10/tarfile.py", line 1639, in open
    raise ReadError(f"file could not be opened successfully:\n{error_msgs_summary}")
tarfile.ReadError: file could not be opened successfully:
- method gz: ReadError('empty file')
- method bz2: ReadError('not a bzip2 file')
- method xz: ReadError('not an lzma file')
- method tar: ReadError('empty file')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/niccololaurenti/n3pdf/nnpdfgit/nnpdf/n3fit/src/n3fit/scripts/n3fit_exec.py", line 271, in run
    super().run()
  File "/home/niccololaurenti/n3pdf/nnpdfgit/nnpdf/validphys2/src/validphys/app.py", line 156, in run
    super().run()
  File "/home/niccololaurenti/miniconda3/envs/nnpdf-dev/lib/python3.10/site-packages/reportengine/app.py", line 380, in run
    rb.execute_sequential()
  File "/home/niccololaurenti/miniconda3/envs/nnpdf-dev/lib/python3.10/site-packages/reportengine/resourcebuilder.py", line 166, in execute_sequential
    result = self.get_result(callspec.function,
  File "/home/niccololaurenti/miniconda3/envs/nnpdf-dev/lib/python3.10/site-packages/reportengine/resourcebuilder.py", line 175, in get_result
    fres =  function(**kwdict)
  File "/home/niccololaurenti/n3pdf/nnpdfgit/nnpdf/n3fit/src/n3fit/performfit.py", line 255, in performfit
    result = pdf_gen_and_train_function(parameters)
  File "/home/niccololaurenti/n3pdf/nnpdfgit/nnpdf/n3fit/src/n3fit/model_trainer.py", line 884, in hyperparametrizable
    photons=Photon(
  File "/home/niccololaurenti/n3pdf/nnpdfgit/nnpdf/validphys2/src/validphys/photon/compute.py", line 70, in __init__
    self.produce_interpolators()
  File "/home/niccololaurenti/n3pdf/nnpdfgit/nnpdf/validphys2/src/validphys/photon/compute.py", line 231, in produce_interpolators
    self.photons_array = [self.compute_photon_array(i) for i in range(len(self.replicas_id))]
  File "/home/niccololaurenti/n3pdf/nnpdfgit/nnpdf/validphys2/src/validphys/photon/compute.py", line 231, in <listcomp>
    self.photons_array = [self.compute_photon_array(i) for i in range(len(self.replicas_id))]
  File "/home/niccololaurenti/n3pdf/nnpdfgit/nnpdf/validphys2/src/validphys/photon/compute.py", line 198, in compute_photon_array
    with EKO.edit(self.path_to_eko_photon) as eko:
  File "/home/niccololaurenti/miniconda3/envs/nnpdf-dev/lib/python3.10/site-packages/eko/io/struct.py", line 923, in edit
    eko = cls.open(path, "a")
  File "/home/niccololaurenti/miniconda3/envs/nnpdf-dev/lib/python3.10/site-packages/eko/io/struct.py", line 876, in open
    cls.load(path, tmpdir)
  File "/home/niccololaurenti/miniconda3/envs/nnpdf-dev/lib/python3.10/site-packages/eko/io/struct.py", line 856, in load
    raise exceptions.OutputNotTar(f"Not a valid tar archive: '{tarpath}'")
eko.io.exceptions.OutputNotTar: Not a valid tar archive: '/home/niccololaurenti/miniconda3/envs/nnpdf-dev/share/NNPDF/data/theory_522/eko_photon.tar'

I'm getting it when I try to evolve the photon from 100 GeV to fitting scale.
Previously I got this error only for some replicas and this made me believe that, being all the replicas computed in parallel, it was trying to load and reshape the eko at the same time for more than one replica. However, this time all the replicas failed.

In any case this is not super urgent since the reshape wasn't really done because the final xgrid was the same of the eko I was trying to reshape (it was just done for control), so I can just load it with read.