Looks like this package is already merged into python3 - https://docs.python.org/3/library/plistlib.html
import plistlib
file_name = "/Library/Preferences/com.apple.TimeMachine.plist"
with open(file_name, 'rb') as infile:
plist = plistlib.load(infile)
print(plist["LastConfigurationTraceDate"])