Merge branch 'python3' into 'master'

Add Python3 compatibility

See merge request !156
5 jobs for master in 24 minutes and 49 seconds
Status Name Job ID Coverage
  Test
passed test_min #253642

00:06:11

passed test_mpi #253643

00:08:43

passed test_mpi_fftw #253644

00:09:01

passed test_mpi_fftw_hdf5 #253645

00:17:47

66.0%
 
  Release
passed release_image_master #253646

00:07:02