Some Nexus 6P owners are reporting battery early shutdown issues with their devices, and have taken to Reddit to discuss the issue. According to the thread where the initial post has brought up the problem, it's also suggested that anyone who is experiencing the issue should report it directly to Google so they become more aware of the problem's existence. While it's certainly not uncommon for phones to drain battery life rather fast then shut down, the issue here is that people's phones are shutting down just as they would if they were out of battery and needing a recharge, but with the phone's batteries still being around 39% - 48%. Some users are reporting their devices shutting down around 17%.
This might not be an issue every single time it happens, as you could be sitting in the comfort of your own home on the couch watching the latest on Netflix, but for some users it's been more than just a little annoyance. One user that goes by the name of corejava2 on Reddit states that their phone shut down as they were waiting on a ride share, while another user named pixiedonut mentions that they were in the process of trying to request an Uber and the phone shut down just before they could hit the button to order the ride, leaving them stranded in freezing cold weather with no way to contact anyone until they reached a nearby hotel to call a friend.
Over on the AOSP issue tracker where users are reporting the issue to Google, the initial poster mentions that they started having the problem after updating their Nexus 6P to Android Nougat. This seems to suggest that the Nougat update may be causing the issue for some users (but not all), although there is no definitive explanation yet as to the cause. Having said that, more than one user notes that they had only started experiencing the issue after the update to Android Nougat, so there is a chance that the update has something to do with it. The problem was initially reported back on November 16th, with a response from Google a few days later stating that they have passed the issue onto the development team to look into it. So far it doesn't appear that Google has updated the post with new information as to the cause or if a fix is incoming to correct the problem.