docker: enable utf8 in Ubuntu Docker images

tools/docker/Dockerfile.test_formatting

@@ -7,6 +7,10 @@ WORKDIR /workspace
 COPY ./scripts/install_basics.sh .
 RUN ./install_basics.sh
 
+# set a proper unicode-enabled locale, see https://hub.docker.com/_/ubuntu?tab=description
+RUN localedef -i en_US -c -f UTF-8 -A /usr/share/locale/locale.alias en_US.UTF-8
+ENV LANG en_US.UTF-8
+
 COPY ./scripts/install_formatting.sh .
 RUN ./install_formatting.sh
 

tools/docker/Dockerfile.test_python

@@ -7,10 +7,14 @@ WORKDIR /workspace
 COPY ./scripts/install_basics.sh .
 RUN ./install_basics.sh
 
+# set a proper unicode-enabled locale, see https://hub.docker.com/_/ubuntu?tab=description
+RUN localedef -i en_US -c -f UTF-8 -A /usr/share/locale/locale.alias en_US.UTF-8
+ENV LANG en_US.UTF-8
+
 COPY ./scripts/install_python.sh .
 RUN ./install_python.sh
 
 COPY ./scripts/ci_entrypoint.sh ./scripts/test_python.sh ./
 CMD ["./ci_entrypoint.sh", "./test_python.sh"]
 
-#EOF
+#EOF

tools/toolchain/Dockerfile

@@ -15,6 +15,10 @@ USER root
 COPY ./install_requirements*.sh ./
 RUN ./install_requirements.sh ${BASE_IMAGE}
 
+# set a proper unicode-enabled locale, see https://hub.docker.com/_/ubuntu?tab=description
+RUN localedef -i en_US -c -f UTF-8 -A /usr/share/locale/locale.alias en_US.UTF-8
+ENV LANG en_US.UTF-8
+
 # copy helper scripts
 WORKDIR /opt/cp2k-toolchain
 RUN mkdir scripts

tools/toolchain/install_requirements_ubuntu.sh

@@ -21,6 +21,7 @@ apt-get install -qq --no-install-recommends \
     git                                     \
     less                                    \
     libtool                                 \
+    locales                                 \
     make                                    \
     nano                                    \
     patch                                   \