pgadmin4 beta 1 blocked

Hi all,
after installing pgadmin4 beta 1 wheel and trying to execute it the
program stucks. Enabling a verbose trace I got it hangs up on:

% python -v ./pgadmin4.py
...
# /usr/lib/python2.7/BaseHTTPServer.pyc matches
/usr/lib/python2.7/BaseHTTPServer.py
import BaseHTTPServer # precompiled from /usr/lib/python2.7/BaseHTTPServer.pyc


and nothing else happens.
Any idea?

Thanks,
Luca