This is a known issue: https://issuetracker.google.com/issues/63253097
Further to my question about getting Google KMS working with App
For me, these messages appear to originate from a GAE (.local) file called stubs.py.
In my first case, stubs.py was looking for files that were not there. So you might want to check to see if "/usr/lib/Acrobat8/Resource/CMap" actually exists. Then, starting with stubs.py, try to find out what file is trying to load it.
My project is using web.py, all of a sudden I started getting (stubs.py) messages again, this time about .pyc files. I put a skip_files: in the bottom of my app.yaml file, and it does suppress the messages, but I haven't tested to see if my app still fully compiles.
skip_files:
- ^(.*/)?\.pyc$
More on the Python GAE runtime and sandbox here. https://cloud.google.com/appengine/docs/standard/python/runtime