It is confusing for users when the pywikibot.Bot gives warnings about self._site not being set. Currently in image.py it gives:
>pwb.py image "Senior picture.jpg" WARNING: Bot.site was not set before being retrieved. WARNING: Using the default site: meta:meta Retrieving 1 pages from meta:meta. WARNING: Bot.site was not set before being retrieved. WARNING: Using the default site: meta:meta
This can be simplified by just setting self.site in the constructor of the Bot class being used by image.py
Marking as good first task, as it's simple to do and would be beneficial for new contributors.