Default to Drush 8 for both Drupal 7 & 8 because dev-master now needs PHP 5.5+

[dsnopek]

We run the Panopoly tests on PHP 5.4, 5.5 & 5.6 - although, mostly through PHP 5.4 because we want to make sure we work with the lowest PHP version possible capable of running our tests.

Suddenly, tests started failing on PHP 5.4 because drush/drush:dev-master now requires PHP 5.5+:

http://docs.drush.org/en/master/install/#drupal-compatibility

In order for tests to continue working with PHP 5.4 (which is also the minimum for Drupal 8), we should default to installing Drush 8 for both Drupal 7 and 8.

[LionsAd]

Thanks, @dsnopek. That makes perfect sense.

[taz77]

Need a new version of Drupal TI for this. The current installation instructions are failing because of the Drush dev-master is broken. I was unsuccessful changing the Drush version via the env variable. But this patch worked.

[dsnopek]

Yeah, unfortunately, the environment overwrites any manual setting of the variable. In Panopoly, we're using the dev version of drupal_ti (rather than a release), which fixed our tests.

[taz77]

Yeah same here. Using dev-master for a fix. Drush dev-master blew up all of my builds in the last 48 hours.

[LionsAd]

@dsnopek @taz77 I guess you all would favor a new release very much, right?

[taz77]

@LionsAd A new release would fix it. There is a bug in Drush dev-master right now that has caused my issue. It was downloading ctools and rules to ~/.drush rather than the bootstrapped Drupal directory. The change committed here (specifying Drush 8.x release) fixed my issue. The issue #69 could also possibly be fixed by this commit. So I would say a new release may fix three issues at once.