Re: [PATCH v2 3/4] travis-ci: check AsciiDoc/AsciiDoctor stderr output

Lars Schneider writes: > Ensure that nothing is written to stderr during a documentation build. I guess we'll know if any output to stderr is an error, or if there are some informational output that would trigger failure from this change soon enough. Will queue.

[PATCH v2 3/4] travis-ci: check AsciiDoc/AsciiDoctor stderr output

`make` does not necessarily fail with an error code if Asciidoc/AsciiDoctor encounters problems. Anything written to stderr might be a better indicator for problems. Ensure that nothing is written to stderr during a documentation build. The redirects do not work in `sh`, therefore the script