Reduce build log verbosity on Travis (#6597)

PR #6568 removed the --quiet option in pip invocations, because this option deletes a lot of extremely useful logs when something goes wrong. However, when everything goes right, or at least when pip install is correctly executed, theses logs add hundreds of lines that are only noise, making hard to debug errors that can be in only one or two lines.

We can have best of both worlds. Travis allows to fold large blocks of logs, that can be expanded directly from the UI if needed. It only requires to print in the console some specific code, that this PR implements in the pip_install.py script when the build is run in Travis (known by the existence of TRAVIS environment variable).

I also take the occasion to clean up a little tox.ini.

Note that AppVeyor does not have this fold capability, but it can be emulated using a proper capture of stdout/stderr delivered only when an error is detected.

* Fold pip install log on travis

* Global test env

* Export env variable

1 files changed, 1 insertions, 0 deletions

diff --git a/.travis.yml b/.travis.yml
index 2b8eafc13..89885d08e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -9,6 +9,7 @@ before_install:
 
 before_script:
   - 'if [ $TRAVIS_OS_NAME = osx ] ; then ulimit -n 1024 ; fi'
+  - export TOX_TESTENV_PASSENV=TRAVIS
 
 matrix:
   include: