Running n3fit crash

Created by: rabah-khalek

@scarlehoff , @Zaharid , @scarrazza Running:

conda create -n n3fit-dev
conda activate n3fit-dev
conda install nnpdf-tf

cd nnpdf
git checkout n3fit
python setup.py develop

n3fit runcards/Basic_runcard.yml 1

crashes with:

OMP: Error #15: Initializing libiomp5.dylib, but found libiomp5.dylib already initialized.
OMP: Hint: This means that multiple copies of the OpenMP runtime have been linked into the program. That is dangerous, since it can degrade performance or cause incorrect results. The best thing to do is to ensure that only a single OpenMP runtime is linked into the process, e.g. by avoiding static linking of the OpenMP runtime in any library. As an unsafe, unsupported, undocumented workaround you can set the environment variable KMP_DUPLICATE_LIB_OK=TRUE to allow the program to continue to execute, but that may cause crashes or silently produce incorrect results. For more information, please see http://www.intel.com/software/products/support/.
Fatal Python error: Aborted

Thread 0x000000010b7225c0 (most recent call first):
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/tensorflow/python/client/session.py", line 1439 in __call__
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/keras/backend/tensorflow_backend.py", line 2675 in _call
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/keras/backend/tensorflow_backend.py", line 2715 in __call__
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/keras/engine/training_arrays.py", line 199 in fit_loop
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/keras/engine/training.py", line 1039 in fit
  File "/Users/rabah/Documents/nnpdf/n3fit/n3fit/ModelTrainer.py", line 378 in _train_and_fit
  File "/Users/rabah/Documents/nnpdf/n3fit/n3fit/ModelTrainer.py", line 469 in hyperparametizable
  File "/Users/rabah/Documents/nnpdf/n3fit/n3fit/fit.py", line 215 in fit
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/reportengine/resourcebuilder.py", line 175 in get_result
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/reportengine/resourcebuilder.py", line 168 in execute_sequential
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/reportengine/app.py", line 359 in run
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/validphys/app.py", line 143 in run
  File "/Users/rabah/Documents/nnpdf/n3fit/n3fit/n3fit.py", line 163 in run
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/lib/python3.7/site-packages/reportengine/app.py", line 374 in main
  File "/Users/rabah/Documents/nnpdf/n3fit/n3fit/n3fit.py", line 174 in main
  File "/Users/rabah/Documents/miniconda3/envs/n3fit-dev/bin/n3fit", line 11 in <module>
[1]    88643 abort      n3fit runcards/Basic_runcard.yml 1

A problem with OpenMP it seems: OMP: Hint: This means that multiple copies of the OpenMP runtime have been linked into the program. That is dangerous, since it can degrade performance or cause incorrect results. The best thing to do is to ensure that only a single OpenMP runtime is linked into the process, e.g. by avoiding static linking of the OpenMP runtime in any library. As an unsafe, unsupported, undocumented workaround you can set the environment variable KMP_DUPLICATE_LIB_OK=TRUE to allow the program to continue to execute, but that may cause crashes or silently produce incorrect results. For more information, please see http://www.intel.com/software/products/support/. Fatal Python error: Aborted