"ModuleNotFoundError: No module named 'unitgrade.dashboard.dashboard_cli'" in command-line program

Executing unitgrade from the command-line generates an error:

$ unitgrade
Traceback (most recent call last):
  File "/usr/local/bin/unitgrade", line 5, in <module>
    from unitgrade.dashboard.dashboard_cli import main
ModuleNotFoundError: No module named 'unitgrade.dashboard.dashboard_cli'