Hi,

Here's my second attempt to fix the issue. I'll wait a few days for
comments before merging, to try and avoid causing a bug like last time.

It turns out the problem was deeper than just the :var argument,
multiline strings in the body were also getting mangled. For example,
this block had the same problem as the original report:

#+begin_src python
  text = """a
  b
  c
  """
  return text
#+end_src

#+RESULTS:
: a
: 	b
: 	c

My fix this time was to use functions from python.el to indent, and to
detect whether we are in a string and shouldn't be indented.

I also added a couple more unit tests, one for multiline strings, and
one for the variable scope/assignment issue that Matt reported.

Cheers,
Jack