Control the logging level in the CLI

[Stannislav]

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Regarding tracebacks / debugging, there are for sure different options.

First of all, we already have a way because we added the __main__.py file. So now to debug some atldld <command> command one just needs to write python -m pdb -m atldld <command>. (I think one needs at least py37...)

And yes I've seen people using CLI flags to control the debug output. One could add something like --debug, --log-level, -v/-vv/-vvv directly to the root atldld command. For logging it would then configure the logging accordingly:

import logging


logger = logging.getLogger(__name__)

@click.group()
@click.option('-v', '--verbose', count=True)
def root(verbose):
    """Run the command line interface for Atlas-Download-Tools."""
    if verbose == 0:
        log_level = logging.WARNING
    elif verbose == 1:
        log_level = logging.INFO
    else:  # verbose >= 2:
        log_level = logging.DEBUG
    logging.basicConfig(level=log_level)

    if verbose > 2:
        logger.warning("The maximal verbosity is -vv")


@root.command("test")
def test():
    logger.critical("Critical")
    logger.error("Error")
    logger.warning("Warning")
    logger.info("Info")
    logger.debug("Debug")

$ atldld test
CRITICAL:atldld.cli:Critical
ERROR:atldld.cli:Error
WARNING:atldld.cli:Warning

$ atldld -v test
CRITICAL:atldld.cli:Critical
ERROR:atldld.cli:Error
WARNING:atldld.cli:Warning
INFO:atldld.cli:Info

$ atldld -vv test
CRITICAL:atldld.cli:Critical
ERROR:atldld.cli:Error
WARNING:atldld.cli:Warning
INFO:atldld.cli:Info
DEBUG:atldld.cli:Debug

$ atldld -vvv test
WARNING:atldld.cli:The maximal verbosity is -vv
CRITICAL:atldld.cli:Critical
ERROR:atldld.cli:Error
WARNING:atldld.cli:Warning
INFO:atldld.cli:Info
DEBUG:atldld.cli:Debug

Originally posted by @Stannislav in https://github.com/BlueBrain/Atlas-Download-Tools/pull/66#discussion_r698353401