Bump shellcheck to 0.8.0

Dockerfile

@@ -7,9 +7,10 @@ RUN export DEBIAN_FRONTEND=noninteractive && \
 
 RUN pip install -U flake8 pylint lxml ast-to-xml requests
 
+ARG SHELLCHECK_VERSION=0.8.0
 RUN mkdir -p /opt/shellcheck && \
     cd /opt/shellcheck && \
-    curl -LO https://github.com/koalaman/shellcheck/releases/download/v0.7.2/shellcheck-v0.7.2.linux.x86_64.tar.xz && \
+    curl -LO "https://github.com/koalaman/shellcheck/releases/download/v${SHELLCHECK_VERSION}/shellcheck-v${SHELLCHECK_VERSION}.linux.x86_64.tar.xz" && \
     tar -xf *.tar.xz --strip-components=1 && \
     rm *.tar.xz && \
     ln -s /opt/shellcheck/shellcheck /usr/bin