demos: py_simple: Fixes.

* Fix compatibility with python 2.6

* Various small fixes.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
pywrap: core: CallbackProxy: Reword error message.

The error happens in general case, not only on parse error.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
build: pywrap.mk: Two fixes.

* Rebuild the so libs when configure was runned.
  (path to the python config could changed)

* Remove redundand -I (I'm suprised it compiled fine before)

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
demos: py_simple: Remove broken plot.py.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>