[PATCH 2/2] travis: build HTML docs

[Bin Meng]

On Fri, Feb 21, 2020 at 11:27 AM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> Several patches delivered incorrect restructured text as documentation.
> We should be able to discover this in Travis CI.
>
> Provide a build step for 'make htmldocs'.
>
> Add required package graphviz.
>
> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
> ---
>  .travis.yml | 5 +++++
>  1 file changed, 5 insertions(+)
>

Reviewed-by: Bin Meng <bmeng.cn at gmail.com>