Not sure why it is in the module shutil, but it landed there in Python 3.3. See:
Querying the size of the output terminal
>>> import shutil
>>> shutil.get_terminal_size((80, 20)) # pass fallback
os.terminal_size(columns=87, lines=23) # returns a named-tuple
A low-level implementation is in the os module. Cross-platform—works under Linux, Mac OS, and Windows, probably other Unix-likes. There’s a backport as well, though no longer relevant.