When no extension items were matched by the input regex, we previously
ran into a runtime error that wasn't obvious. Instead print an error
message explaining what the problem is.

In some cases, `item_statuses` can be shorter than
`item_names_versions`. I didn't look into why, just decided to add a
quick fix for the bounds error so the program could keep working again
without crashing. This seems to fix the problem I had, but it may need
to be revisited further down the line.

Sometimes I was getting the following exception which caused the program
to fail:

    $ cws-status 'AODocs - Universal'
    Traceback (most recent call last):
      File ".../cws-status/cws-status", line 117, in <module>
        matched_extensions.append((name, item_statuses[i]))
    IndexError: list index out of range

Add a couple of print statements to see what's going on.

There's another instance when the user can be logged out and the "Sign
in to continue" string doesn't appear on the page. Also report this as a
logged out error.

I tried catching the `argparse.ArgumentError` as described here, but
that didn't seem to work:
https://docs.python.org/3.9/library/argparse.html#exit-on-error

When I wrapped `args = argparser.parse_args()` in a `try` block, it
raised a `SystemExit` exception instead of `argparse.ArgumentError`.

Take inspiration from some of the suggestions in this Stack Overflow
answer:
https://stackoverflow.com/questions/5943249/python-argparse-and-controlling-overriding-the-exit-status-code

Since we just want to change the exit code, call
`argparse.ArgumentParser`'s `error()` method and exit with the error
code we want.

Rather than output a single tab to separate the extension name and
version, use `ljust` to create two visual columns.