Use shutil.get_terminal_size(); requires python 3.3

Python 3.3 was released in September 2012 and end of life in September
2017.

README.rst

@@ -8,7 +8,7 @@ Ydiff
 Term based tool to view *colored*, *incremental* diff in a version controlled
 workspace (supports Git, Mercurial, Perforce and Svn so far) or from stdin,
 with *side by side* (similar to ``diff -y``) and *auto pager* support. Requires
-python >= 3.0 and ``less`` as a pager.
+python >= 3.3 and ``less`` as a pager.
 
 See screenshots below.
 

ydiff.py

@@ -8,11 +8,10 @@
 """
 
 import difflib
-import fcntl
 import os
 import re
+import shutil
 import signal
-import struct
 import subprocess
 import sys
 import termios
@@ -29,8 +28,8 @@
                      'stdin, with side by side and auto pager support')
 }
 
-if sys.hexversion < 0x03000000:
-    raise SystemExit('*** Requires python >= 3.0.0')    # pragma: no cover
+if sys.hexversion < 0x03030000:
+    raise SystemExit('*** Requires python >= 3.3.0')    # pragma: no cover
 
 
 class Color(object):
@@ -710,15 +709,8 @@ def decode(octets):
 
 
 def terminal_width():
-    """Returns terminal width. Taken from https://gist.github.com/marsam/7268750
-    but removed win32 support which depends on 3rd party extension. Will raise
-    IOError or AttributeError when impossible to detect.
-    """
-    s = struct.pack('HHHH', 0, 0, 0, 0)
     try:
-        x = fcntl.ioctl(1, termios.TIOCGWINSZ, s)
-        _, width = struct.unpack('HHHH', x)[0:2]  # height unused
-        return width
+        return shutil.get_terminal_size().columns
     except Exception:
         return 80