Do not install Sphinx explicitly

Including the Sphinx package in the "pip3 install" invocation causes the
docutils version requirements specified by sphinx-rtd-theme (< 0.17) to
be overridden by those specified by Sphinx (< 0.18, >= 0.14), resulting
in version 0.17.1 of docutils being installed, which is incompatible
with the latest version of sphinx-rtd-theme (0.5.2).

As sphinx-rtd-theme depends on the Sphinx package anyway, only include
the former in the "pip3 install" invocation to ensure a compatible
version of docutils is installed in the relevant Docker image.

docker/bind9/debian-template/Dockerfile

@@ -143,7 +143,7 @@ RUN if [ "@RESPDIFF@" = "yes" ]; then apt-get -y install python3-dpkt python3-lm
 RUN if [ "@SHELLCHECK@" = "yes" ]; then apt-get -y install shellcheck; fi
 RUN if [ "@SOFTHSM@" -ge "2" ] 2>/dev/null; then apt-get -y install libsofthsm2 softhsm2; fi
 RUN if [ "@SOFTHSM@" -lt "2" ] 2>/dev/null; then apt-get -y install libsofthsm softhsm; fi
-RUN if [ "@SPHINX@" = "yes" ] 2>/dev/null; then pip3 install Sphinx sphinx-rtd-theme && apt-get -y install texlive-full texlive-xetex xindy; fi
+RUN if [ "@SPHINX@" = "yes" ] 2>/dev/null; then pip3 install sphinx-rtd-theme && apt-get -y install texlive-full texlive-xetex xindy; fi
 COPY kyua.tar /
 RUN if [ ! -s /kyua.tar ]; then \
 	curl -sSL "https://github.com/jmmv/atf/releases/download/atf-${ATF_VERSION}/atf-${ATF_VERSION}.tar.gz" | tar -xz -C /usr/src && \