Core: Provide a better error message if only weights.yaml is provided with players: 0

[remyjette]

What is this fixing or adding?

A user in the discord had some confusion because they had named their player YAML file weights.yaml. Since this is the generic weights file and the user had not specified the number of players or provided any other files, the number of players was 0. But, since there was a weights file, the if not weights_cache: check did not raise an Exception. It wasn't until checking for slot name uniqueness that things blew up, with a very confusing error.

How was this tested?

Put a weights.yaml in the Players folder and ran Generate.py.

Before:

Archipelago (0.4.3) logging initialized on Linux-6.2.0-1012-azure-x86_64-with-glibc2.35 running Python 3.10.12
Weights: /home/remyjette/Archipelago/Players/weights.yaml >> Simple archipelago game YAML
Generating for 0 player, 19738373992647940205 Seed 79421069723667378462 with plando: bosses
Uncaught exception
Traceback (most recent call last):
  File "/home/remyjette/Archipelago/Generate.py", line 646, in <module>
    main()
  File "/home/remyjette/Archipelago/Generate.py", line 202, in main
    if len(set(name.lower() for name in erargs.name.values())) != len(erargs.name):
AttributeError: 'Namespace' object has no attribute 'name'

After:

Archipelago (0.4.3) logging initialized on Linux-6.2.0-1012-azure-x86_64-with-glibc2.35 running Python 3.10.12
Weights: /home/remyjette/Archipelago/Players/weights.yaml >> Simple archipelago game YAML
Uncaught exception
Traceback (most recent call last):
  File "/home/remyjette/Archipelago/Generate.py", line 651, in <module>
    main()
  File "/home/remyjette/Archipelago/Generate.py", line 132, in main
    raise Exception("No individual player files found and number of players is 0. "
Exception: No individual player files found and number of players is 0. Provide individual player files or specify the number of players via host.yaml or --multi.