augur --help crashes: cli/csv_utils.py has no cli attribute (MultiCommand import issue)

[sohampirale]

Description

Running augur --help crashes due to a CLI module being imported that does not define a cli command.

Steps to Reproduce
make install
augur --help

Actual Result

augur --help throws:

AttributeError: module 'augur.application.cli.csv_utils' has no attribute 'cli'

Cause (likely)

augur/application/cli/_multicommand.py lists every non-underscored .py file in augur/application/cli/ as a command module, but csv_utils.py appears to be a utility/helper module and does not define cli.

Suggested Fix

In _multicommand.py, either:

skip utility modules like *_utils.py in list_commands(), or

make get_command() safely return None when a module has no cli attribute (instead of raising an exception).

[MoralCode]

there is now an issue for this here: #3627