Remove python2.5 support from texmanager.py

closes matplotlib#1552

Author: NelleV

lib/matplotlib/texmanager.py

@@ -43,10 +43,7 @@
 import sys
 from subprocess import Popen, PIPE, STDOUT
 
-try:
-    from hashlib import md5
-except ImportError:
-    from md5 import md5  # Deprecated in 2.5
+from hashlib import md5
 
 import distutils.version
 import numpy as np