Set explicit locale on fedora 30 testing container

dev/containers/fedora-pip-py3

@@ -18,7 +18,8 @@ RUN dnf -y install \
     gcc \
     redis \
     which \
-    git
+    git \
+    glibc-langpack-en
 
 RUN cd / \
     && git clone -b $BRANCH $REPO \

dev/containers/tox_py3.sh

@@ -22,4 +22,5 @@ echo "Last commits:"
 git --no-pager log -2
 fi
 
+export LANG="en_US.UTF-8"
 tox -v --sitepackages -e 'py35-flask100-ci' -- --results=results