How do I skip an Android system update and stop its notifications? I get a message

Android 5.0.1 System Update Available


but no option to skip the update.

In frustration, I click "download". It's not better after the download. I still get

System update downloaded


with no option to avoid the update.

How do I signal that I am perfectly content with KitKat 4.4.4 for the time being? I use my phone for development and want to be certain my development tools are ready before upgrading. In the meantime I also want to stop  the continuous harassment via notifications. Is this possible? I am using a Nexus 5 and the phone is not rooted (I prefer it to stay that way).
I just spoke to Google directly. The Nexus 5 under settings, apps has something called Google Play services. Not store. If you uncheck the notification box in Google Play services and restart the phone the notification for the Android system updates will stop in the notification bar. Worked like a charm!