Comment 16 for bug 1482844

python3-xlib_0.14+20091101-1ubuntu3_all.deb didn't solve the issue. I receive:

Traceback (most recent call last):
  File "/usr/bin/caffeine", line 36, in <module>
    ewmh = EWMH()
  File "/usr/lib/python3/dist-packages/ewmh.py", line 50, in __init__
    self.display = _display or display.Display()
  File "/usr/lib/python3/dist-packages/Xlib/display.py", line 80, in __init__
    self.display = _BaseDisplay(display)
  File "/usr/lib/python3/dist-packages/Xlib/display.py", line 62, in __init__
    display.Display.__init__(*(self, ) + args, **keys)
  File "/usr/lib/python3/dist-packages/Xlib/protocol/display.py", line 129, in __init__
    raise error.DisplayConnectionError(self.display_name, r.reason)
Xlib.error.DisplayConnectionError: Can't connect to display ":0": b'Invalid MIT-MAGIC-COOKIE-1 key'

Old python3-xlib_0.14+20091101-1ubuntu2_all.deb returns:

Traceback (most recent call last):
  File "/usr/bin/caffeine", line 36, in <module>
    ewmh = EWMH()
  File "/usr/lib/python3/dist-packages/ewmh.py", line 50, in __init__
    self.display = _display or display.Display()
  File "/usr/lib/python3/dist-packages/Xlib/display.py", line 80, in __init__
    self.display = _BaseDisplay(display)
  File "/usr/lib/python3/dist-packages/Xlib/display.py", line 62, in __init__
    display.Display.__init__(*(self, ) + args, **keys)
  File "/usr/lib/python3/dist-packages/Xlib/protocol/display.py", line 129, in __init__
    raise error.DisplayConnectionError(self.display_name, r.reason)
Xlib.error.DisplayConnectionError: Can't connect to display ":0": b'No protocol specified\n'

ubuntu 14.04 lts with 3.19.0-30-generic kernel from vivid and xserver-xorg-lts-vivid 1:7.7+7ubuntu3~trusty1