fix doctests in cpim.py

Ignore-this: d4c12998c41085ea2c6304900ff0ee65

darcs-hash:20090203101853-b2873-fd2b611f83cd19059da35d5cc35ae9f8465fff36
green.engine minor fix: poorly placed assert could be raised falsely

Ignore-this: 945bde1d754b8a7e96b9db38ef1a2e26

darcs-hash:20090203101938-b2873-6df76c5e0a58f0901d597c0c05fbce9ee2a5daaf