Flush stdout everywhere on Travis to avoid out-of-order output

[asmeurer]

#322

I haven't fixed it yet. I'm using this branch to debug it.

[asmeurer]

I tried to reproduce it on my fork and I couldn't asmeurer/xonsh#1

[asmeurer]

OK, my PR build at https://travis-ci.org/asmeurer/xonsh/jobs/424980715 literally merges the exact same two commits together as the failing build from the issue, and it doesn't reproduce the issue.

[asmeurer]

Maybe I need to have doctr enabled or else it won't run.

[asmeurer]

Turns out this was an issue with the xonsh .travis.yml. However, I like having flushing to keep the output in order. You can see from the failing build that for instance "The website and docs are not pushed to gh-pages on pull requests" is printed at the end after the git stash pop, when it should be printed from this function. So I'm going to merge this PR anyway.

[asmeurer]

Oh it still happens. I guess it has to do with the way Travis mixes stdout and stderr.

[asmeurer]

I don't think this will help. The problem is that Travis doesn't output stderr alongside stdout like you would get in a terminal, even with flushing. Probably we should avoid using stderr on Travis, since it doesn't do anything anyway (but other things like tracebacks being out of order can't be helped).