Fix the supervisord template.

The script was relying on the presence of an environment variable, which
is only set when the virtualenv is activated. But a virtualenv does not
have to be activated to work (it's possible to call the python command
directly).

This fixes it by relying on `sys.executable` which should be correct at
all times.

Fixes #306

ihatemoney/conf-templates/supervisord.conf.j2

@@ -1,5 +1,5 @@
 [program:ihatemoney]
-command={{ venv_path }}/bin/gunicorn -c /etc/ihatemoney/gunicorn.conf.py ihatemoney.wsgi:application
+command={{ bin_path }}/gunicorn -c /etc/ihatemoney/gunicorn.conf.py ihatemoney.wsgi:application
 user=ihatemoney
 autostart=true
 autorestart=true

ihatemoney/manage.py

@@ -49,9 +49,11 @@ class GenerateConfig(Command):
             os.path.join('conf-templates/', config_file) + '.j2'
         ).decode('utf-8')
 
+        bin_path = os.path.dirname(sys.executable)
+
         print(Template(template_content).render(
                 pkg_path=os.path.abspath(os.path.dirname(__file__)),
-                venv_path=os.environ.get('VIRTUAL_ENV'),
+                bin_path=bin_path,
                 secret_key=self.gen_secret_key(),
         ))