Some sphinx require latexmk

Author: jnothman

.travis.yml

@@ -12,7 +12,7 @@ cache:
   directories:
     - $HOME/.cache/pip
 before_install:
-  - sudo apt-get install texlive texlive-latex-extra
+  - sudo apt-get install texlive texlive-latex-extra latexmk
   - pip install --upgrade pip setuptools  # Upgrade pip and setuptools to get ones with `wheel` support
   - pip install --find-links http://wheels.astropy.org/ --find-links http://wheels2.astropy.org/ --trusted-host wheels.astropy.org --trusted-host wheels2.astropy.org --use-wheel nose numpy matplotlib ${SPHINX_SPEC}
 script: