Cannot use magento package manager, error 500 blank page

[zelik888]

If I use PHP7, I cannot use the magento package manager, I get an error 500.
Inchoo_php7_test works fine, everything else in the site works as well. I'm on Magento 1.9.3.8.

If i revert to HHVM or php5.6 package manager works. Is this a known problem?