win_pkg: Fix traceback when package is not installed

[terminalmage]

This corrects two calls to list.pop() which don't account for a potentially-empty list. In the first case, the only way that this happens is if pkg.list_pkgs is broken, so it's very unlikely, but I've added logging there just in case to make an issue with pkg.list_pkgs more apparent.

[terminalmage]

I need to take another look at this, I glanced back at the block before this and noticed that the list shouldn't be empty, I'm going to see if there is a better fix.

[terminalmage]

OK it should be good now.

[damon-atkins]

I thought the standard was to use .format(name) this change seems to remove it from the log messages?

log.trace('Sorting out the latest available version of {0}'.format(name))
vs
log.trace('Determining latest installed version of %s', name)

Could this be updated if log.* does not need to use format
https://docs.saltstack.com/en/latest/topics/development/conventions/style.html

[terminalmage]

@damon-atkins I'm not sure what you mean by "standard", to my knowledge there is no standard for log messages.

If you refer to the Python docs, you'll see that printf-style string formatting is already being executed any time a message is logged. The *args are used as input for the % operator under-the-hood. This happens irrespective of whether or not you actually use this syntax. So, using str.format() is (IMO) overkill, since the logging module is already going to do a % string format operation anyway.

[damon-atkins]

There is this statement and then 90% of log messages seem to use format. And the guide says don't use printf which you have indicated is what log does. The aim is to try and remove confusion for my self and I suppose others.

FORMATTING STRINGS
All strings which require formatting should use the .format string method:
data = 'some text'
more = '{0} and then some'.format(data)
Make sure to use indices or identifiers in the format brackets, since empty brackets are not supported by python 2.6.
Please do NOT use printf formatting.

[thatch45]

Using printf for log messages is ok, it is faster and does not typically require the same level of formatting as inline strings.
I need to update our style guide to reflect this. It was also originally written back in the early days on python3 when the verbiage from python was more around "use tons of .format", but that has changed and they are more open to printf support, (Which has also been expanded and made more robust in recent versions of python3)