Travis CI: Run on multiple Fedora versions

Now when we have 3.6 and 3.7, this is important

Author: hroncok

.travis.yml

@@ -3,7 +3,15 @@ sudo: required
 services:
   - docker
 
+env:
+  - FEDORA=27
+  - FEDORA=28
+  - FEDORA=29
+  - FEDORA=rawhide
+
 install:
+  - sed -i "s/fedora-28-x86_64/fedora-${FEDORA}-x86_64/" mock.cfg
+  - sed -i "s|FROM fedora|FROM registry.fedoraproject.org/fedora:${FEDORA}|" Dockerfile
   - docker build -t taskotron .
 
 script:

Dockerfile

@@ -2,7 +2,7 @@ FROM fedora
 
 RUN dnf -y install --setopt=install_weak_deps=false --setopt=tsflags=nodocs \
     --setopt=deltarpm=false python2-rpm python3-rpm tox python2-dnf \
-    python3-dnf mock && dnf clean all
+    python3-dnf mock --allowerasing --best && dnf clean all
 
 ENV LANG=C.UTF-8 LC_ALL=C.UTF-8