Arch Linux

Cinnamon package lacks a dependency on 'python2-ptyprocess'.
The absence of the package prevents cinnamon-settings to launch (see below).

This was exposed on my system by updating the following packages:
[2015-10-25 00:08] [ALPM] upgraded pygobject-devel (3.18.0-1 -> 3.18.2-1)
[2015-10-25 00:08] [ALPM] upgraded python-gobject (3.18.0-1 -> 3.18.2-1)
[2015-10-25 00:08] [ALPM] upgraded python2-gobject (3.18.0-1 -> 3.18.2-1)
[2015-10-25 00:08] [ALPM] upgraded python2-pexpect (3.3-2 -> 4.0.1-1)

$ cinnamon-settings
/usr/lib/cinnamon-settings/cinnamon-settings.py:12: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
from gi.repository import Gio, Gtk, GObject, GdkPixbuf, GLib, Pango, Gdk, cairo
/usr/lib/cinnamon-settings/modules/cs_notifications.py:4: PyGIWarning: Notify was imported without specifying a version first. Use gi.require_version('Notify', '0.7') before import to ensure that the right version gets loaded.
from gi.repository import GObject, Notify
/usr/lib/cinnamon-settings/modules/cs_power.py:4: PyGIWarning: CinnamonDesktop was imported without specifying a version first. Use gi.require_version('CinnamonDesktop', '3.0') before import to ensure that the right version gets loaded.
from gi.repository import CinnamonDesktop, Gdk, UPowerGlib
/usr/lib/cinnamon-settings/modules/cs_power.py:4: PyGIWarning: UPowerGlib was imported without specifying a version first. Use gi.require_version('UPowerGlib', '1.0') before import to ensure that the right version gets loaded.
from gi.repository import CinnamonDesktop, Gdk, UPowerGlib
/usr/lib/cinnamon-settings/modules/cs_user.py:4: PyGIWarning: AccountsService was imported without specifying a version first. Use gi.require_version('AccountsService', '1.0') before import to ensure that the right version gets loaded.
from gi.repository import AccountsService, GLib
Traceback (most recent call last):
File "/usr/lib/cinnamon-settings/cinnamon-settings.py", line 38, in <module>
modules = map(__import__, mod_files)
File "/usr/lib/cinnamon-settings/modules/cs_user.py", line 9, in <module>
import pexpect
File "/usr/lib/python2.7/site-packages/pexpect/__init__.py", line 75, in <module>
from .pty_spawn import spawn, spawnu
File "/usr/lib/python2.7/site-packages/pexpect/pty_spawn.py", line 11, in <module>
import ptyprocess
ImportError: No module named ptyprocess