Merge pull request #2432 from splunk/bugfix/DOCS-999-Missing-lib

DOCS-999 - Fix bug

Author: puribe-splunk

Dockerfile

@@ -8,4 +8,5 @@ RUN apt-get update && \
 RUN pip3 install --upgrade pip
 RUN pip3 install -r requirements.txt --force-reinstall --no-cache-dir --root-user-action=ignore
 RUN pip3 install sphinx-autobuild --root-user-action=ignore
+RUN pip3 install standard-imghdr
 ENTRYPOINT ["tail", "-f", "/dev/null"]