Well, you can do 'elif' in shell, or somehow "or" in [[ test (but that didnt work for me). 
But how do you think I should use it there? I thought we'd keep one statement for the "python version check" and other for "set the _PY27 flag". Otherwise, the code would have to look like this: 
if python2.6
  # do nothing
elif python2.7 
  set _PY27 flag
else
  echo Error, you need python 2.6/2.7. 
fi

-> which is imho longer and not so clear code.