Bug#1138623: persalys FTBFS on big endian: pyinstallcheck_DataModel_load test failure

[Pranav P]

Hi Adrian,

I was looking into this for the past 2 days.
I will just share what all I found.

So, in the `python/test/DataModel.xml` file, the file path for the two csv files (`Housing-prices-Boston.csv` and `table.csv`)
are hard coded like the following `/home/aroles/Documents/proj_persalys/studies/Housing-prices-Boston.csv` and
`/home/aroles/Documents/proj_persalys/studies/table.csv`. This is where the issue starts. Since, this is a hard coded absolute path,
the program doesn't find these files. Hence for line no. 493 in `lib/src/base/DataModel.cxx` in the function call
`ImportedDataset(fileName, inputColumns, outputColumns)`, it throws an exception and goes into the catch block and hence falls
back to the `.h5` file. Now the `.h5` file has entries in little endian format. Hence, in x86 machines, the data is read fine but fails on
s390x. But the thing is, HDF5 files are supposed to be portable across architectures (irrespective of endianness). I can see that the
call is moving into `libOT.so`. So will have to dig deeper over there to see why this is exactly happening.

Meanwhile, I tried correcting the paths (by changing them to relative paths). Now the first assertion (line 14 of `t_DataModel_load.py`)
now passes. This is since that the `.csv` file is being picked up rather than the `.h5` file. But still, the second assertion fails. That is when
I noticed another thing. The file called `table.csv` doesn't exist within the repo. I am not sure whether that is supposed to be produced
by another test case or was supposed to uploaded. But since the file is not there the control falls back to the `.h5` file and chaos
continues.

If there was a `table.csv` file, then changing the path names and uploading this file should fix the issue. Or another work around we
could do is to add the necessary byte swaps in the `t_DataModel_load.py` file.

Thanks,
Pranav