wscript overwrites PYTHONPATH

[EliotBlennerhassett]

If an existing PYTHONPATH is set, this is overwritten in processes spawned from the wscript.

For instance if I install pygccxml in my own directory specified in PYTHONPATH, it can't be found by waf configure.

os.environ['PYTHONPATH'] = os.getcwd()

should be replaced with something like this:

os.environ['PYTHONPATH'] = os.getcwd()+':'+os.environ['PYTHONPATH']
(not sure how to do this in os independent way)