Fix Python 2.5 support

And fix some PEP8 style issues (mostly about spaces) while I was there.

refs #806

tools/install_xdg.py

@@ -1,9 +1,12 @@
 #!/usr/bin/env python
+from __future__ import with_statement
+
 import glob
 import subprocess
 import os
 import sys
 
+
 def check_executable(executable):
     with open('/dev/null', 'w') as devnull:
         process = subprocess.Popen(['which', executable], stdout=devnull)
@@ -14,6 +17,7 @@ def check_executable(executable):
         print >>sys.stderr, 'Error: %s is not installed on your system.' % executable
         sys.exit(1)
 
+
 def install_xdg():
     print 'installing desktop menu files'
     check_executable('xdg-desktop-menu')