docs: def check_module(mod_name):
      """Calls sys.exit() if the module *mod_name* is not found."""
      # Special cases #
      if mod_name in module_name: mod_name = module_name[mod_name]
      # Use a try except block #
      try:
          __import__(mod_name)
      except ImportError as e:
          if str(e) != 'No module named %s' % mod_name: raise e
          print 'You do not seem to have the "%s" package properly installed.' \
                ' Either you never installed it or your $PYTHONPATH is not set up correctly.' \
                ' For more instructions see the README file. (%s)' % (mod_name, e)
          sys.exit()