[Python-mode] py-execute-buffer and CWD

[Andrea Crotti]

While trying to run a script and there is already another *Python* 
buffer open
for another directory, running the script normally fails if there are some
relative file paths.

Apparently the CWD in the *Python* buffer remains the old one, and thus it
makes sense that Python can't resolve relative paths.

I tried to add this line in py-execute-buffer but without success,
any help?

     (cd (file-name-directory (buffer-file-name py-master-file)))