Use logging instead of prints

[paskino]

https://docs.python.org/3/library/logging.html

[gfardell]

If you create logger inside a module with the module name:

import logging
logger = logging.getLogger(__name__)

then output statements as:

logger.info('setting up CGLS')
logger.warning('xinit is deprecated')

we can then have users change the verbosity level they want, the start of the script needs something like:

import logging
logging.basicConfig(level=logging.WARNING)
cil_log_level = logging.getLogger('cil.optimisation.algorithms.CGLS')
cil_log_level.setLevel(logging.DEBUG)

Or the module structure of the names means you can target all the loggers you want at each module level:

logging.basicConfig(level=logging.WARNING)
cil_log_level = logging.getLogger('cil')
cil_log_level.setLevel(logging.INFO)