[JOSS] Unclosed file warning

[Andreas Kloeckner]

Upon running the lid-driven cavity example with $PYTHONWARNINGS=default:

$  ocellaris lid_driven_cavity_flow.inp

I get numerous instances of:

/home/andreask_work/tmp/ocellaris/ocellaris/cpp/__init__.py:17: ResourceWarning: unclosed file <_io.TextIOWrapper name='/home/andreask_work/tmp/ocellaris/ocellaris/cpp/linear_convection.h' mode='rt' encoding='UTF-8'>
  for line in open(os.path.join(cpp_dir, cpp_filename), 'rt'):

[Tormod Landet]

Fixed in master