some example fail because file is not found

../auto/Examples/bayesian/likelihood_sampling.py 
Traceback (most recent call last):
  File "/G/sw/ba/build/../auto/Examples/bayesian/likelihood_sampling.py", line 70, in <module>
    data = ba.readData1D(filepath, ba.csv1D, flags)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/G/sw/ba/build/py/src/bornagain/lib/libBornAgainDevice.py", line 2795, in readData1D
    return _libBornAgainDevice.readData1D(*args)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: BornAgain C++ Exception: File does not exist: specular/genx_alternating_layers.dat.gz

File sits in /testdata/specular/genx_alternating_layers.dat.gz, but is not found.

Similar failures:

• bayesian/likelihood_sampling.py
• fit/specular/Specular1Par.py
• fit/specular/TREFF_Ni_film.py
• and several more in fit/specular
• and several more in fit/scatter

Solution can be found in ../auto/Examples/fit/scatter2d/expfit_galaxi.py, which fails with meaningful message:

Traceback (most recent call last):
  File "/G/sw/ba/build/../auto/Examples/fit/scatter2d/expfit_galaxi.py", line 22, in <module>
    raise Exception("Environment variable BA_DATA_DIR not set")
Exception: Environment variable BA_DATA_DIR not set