[O] left padding added each time a code block is edited

[Noah Hoffman]

Hello,

Each time I edit a code block using =C-c '= (org-edit-special) and then
return to the org-mode buffer, two spaces are added to the left margin of
the code. For example,

#+BEGIN_SRC python
print "hello"
#+END_SRC

becomes

#+BEGIN_SRC python
  print "hello"
#+END_SRC

after one round-trip. This is particularly problematic for python code
blocks since leading whitespace is meaningful.

This is behavior that has been present in org-mode for so long that I
suspect that it's not a bug - but I'd love to know how to disable it.

Thanks a lot,
Noah