Changed in version 3.12: Unrecognized escape sequences produce a SyntaxWarning. In a future Python version they will be eventually a SyntaxError.

I found two places in py-postgressql with this issue.
Unpacking python3-postgresql (1.2.1+git20180803.ef7b9a9-4build5) ...
Setting up python3-postgresql (1.2.1+git20180803.ef7b9a9-4build5) ...
/usr/lib/python3/dist-packages/postgresql/protocol/element3.py:260: SyntaxWarning: invalid escape sequence '\c'
return self.data.strip(b'\c\n\t 0123456789') or None
/usr/lib/python3/dist-packages/postgresql/python/command.py:223: SyntaxWarning: invalid escape sequence '\s'
"Configure environment variables. \set without arguments to show all")
/usr/lib/python3/dist-packages/postgresql/types/init.py:611: SyntaxWarning: invalid escape sequence '*'