I am a great python fan. Recently I got an idea to write RTS engine and/or maybe a simple RTS game based upon this engine. There are a couple of things I need to think about and maybe you can give me some advice on these:

Performance. Most games are written in C++. Isn't python too slow for game engine? I am aiming only at 2D, but still it may be too demnading.
Graphics. Are there any good graphics libraries for python? SDL/OpenGL bindings or maybe something more suitable for python?
Game engines. Do you know of any existing RTS engine written in python?
Any tools/libraries for python that maybe helpful in developing RTS

Thanks in advance!
I can answer your first two.

Python isn't too slow for games.  That all games must be written in C++ is a myth.  Sure C++ (or C) might give you the best performance, but it doesn't mean you're unable to write a game in another language.
Try PyGame: SDL bindings for Python.
2D RTS in Python?