auto install plugin

Default location is ../files/logs but you may have changed it on installation.
You'll find location in your parameters.php file.

OK !

What I can read from log file is that you have issue while deploying the application, not while downloading...
It is because the installation will overwrite all the application files, so PHP user must have write acces to the whole projeqtor directory
Something like :should fix issue.
NB : if you're not on debian like distrib (Ubuntu, ...) change www-data with correct php user, for instance apache for red-hat like litrib (centos,...)