Bug: Mail contrib: Negative indexing is not supported error

Brief summary of issue:

After having implemented the mail.py contrib module, I started to fiddle around with it and saw that after inputting @mail 1 (to check mail with id 1) it would be executed as it should be. However, when you try a negative number, like @mail 0, it would give the Assertion Error: Negative indexing is not supported, which is generated from the django package.

Steps to reproduce the issue:

1. Implement the mail.py module from evennia/contrib
2. Type in ‘@mail 0’ or ‘@mail -42’ for example

Error output

Traceback (most recent call last):
  File "c:\mud\evennia\evennia\commands\cmdhandler.py", line 509, in _run_command
    ret = yield cmd.func()
  File ".\commands\mail.py", line 214, in func
    message = self.get_all_mail()[int(self.lhs) - 1]
  File "c:\mud\pyenv\Lib\site-packages\django\db\models\query.py", line 277, in __getitem__
    "Negative indexing is not supported."
AssertionError: Negative indexing is not supported.

Extra information, such as Evennia revision/repo/branch, operating system and ideas for how to solve:

Happened on rev ae2c2be8, but doesn’t matter which revision as long as the mail.py contrib module is implemented in the system.

[Griatch]

This is because it is trying to index in a queryset, which does not support negative indexing. This should be handled as part of the input verification. Pinging @grungies1138 in case he wants to peek at it.

[Griatch]

I fixed the contrib with more elaborate index error checking. So this should not happen any more. Closing.