Description of problem:
$ dnf info botan2
Fedora 28 - x86_64 - Test Updates                                                                     995 kB/s | 8.2 MB     00:08    
Fedora 28 - x86_64 - Updates                                                                          2.9 kB/s | 257  B     00:00    
Fedora 28 - x86_64                                                                                    1.0 MB/s |  60 MB     01:00    
Last metadata expiration check: 0:00:00 ago on Thu 22 Mar 2018 09:42:22 AM CET.
[Errno 13] Permission denied: '/etc/dnf/modules.d'
exit 1
~> ls -hl /etc/dnf/    
total 12K
-rw-r--r--. 1 root root   72 Feb 12 08:39 dnf.conf
drwxr-xr-x. 2 root root 4.0K Feb 12 16:04 plugins
drwxr-xr-x. 2 root root 4.0K Feb 12 16:04 protected.d


Version-Release number of selected component (if applicable):
~> rpm -qa|grep dnf
dnf-conf-2.7.5-8.fc28.noarch
dnf-yum-2.7.5-8.fc28.noarch
dnf-plugins-core-2.1.5-4.fc28.noarch
dnf-2.7.5-8.fc28.noarch
python2-dnf-2.7.5-8.fc28.noarch
python3-dnf-plugin-system-upgrade-2.0.5-3.fc28.noarch
python3-dnf-plugins-core-2.1.5-4.fc28.noarch
python3-dnf-2.7.5-8.fc28.noarch
libdnf-0.11.1-3.fc28.x86_64
python3-dnf-plugins-extras-common-2.0.5-3.fc28.noarch

How reproducible:
Easy. Upgrade from F27 to F28 and run `dnf info` as normal user.

Steps to Reproduce:
1. Upgrade to F28
2. Run dnf info as normal user

Actual results:
[Errno 13] Permission denied: '/etc/dnf/modules.d'

Expected results:
One can use dnf as normal user without error.

Additional info:
After running sudo dnf info or sudo dnf check-update /etc/dnf/modules.d exists.