Just saw this error and usually this is due to having a misconfiguration in the database connection options. But I am running Fedora 25 with seLinux enabled by default.

First to test if it’s seLinux causing an issue

sudo setenforce 0

If it works fine with seLinux disabled then do the following:

sudo setsebool -P httpd_can_network_connect 1

# turn seLinux back on

sudo setenforce 1

Should now work