install.py has an unhandled corner case when installing with uwsgi support

[cynthia]

If the uwsgi package is not installed (and hence /etc/uwsgi is missing) the installer marches forward without checking if /etc/uwsgi exists as a directory, causing it to prematurely abort.

It should check if the directory is missing before attempting to copy files in the directory. (and probably suggest/attempt) installation if it is missing)