Fixes acquia#3998: Support PHP 7.4 (acquia#3997)

* Bump Travis CI PHP version.

* Bump robo version to support php 7.4.

* debug

* Update .travis.yml

* Drush 10 php 7.4.

.travis.yml

@@ -29,7 +29,7 @@ env:
     # Custom configuration.
     - COMPOSER_BIN=$TRAVIS_BUILD_DIR/vendor/bin
     - BLT_DIR=$TRAVIS_BUILD_DIR
-    - DRUPAL_CORE_HEAD=8.8.x-dev
+    - DRUPAL_CORE_HEAD=8.9.x-dev
     # Change to 1 to debug failed tests.
     - BLT_PRINT_COMMAND_OUTPUT=0
 
@@ -46,6 +46,8 @@ jobs:
     - { name: "Integrated test w/ dev package versions & next minor dev version of Drupal core", env: ORCA_JOB=CORE_NEXT }
     # Custom jobs.
     - env: DRUPAL_CORE_VERSION=default PHPUNIT_EXCLUDE_GROUP='drupal,requires-vm'
+    - env: DRUPAL_CORE_VERSION=default PHPUNIT_EXCLUDE_GROUP='drupal,requires-vm'
+      php: "7.4"
     - env: DRUPAL_CORE_VERSION=default PHPUNIT_GROUP='drupal'
     - env: DRUPAL_CORE_VERSION=$DRUPAL_CORE_HEAD
   allow_failures:

composer.json

@@ -23,15 +23,15 @@
         "composer/semver": "^1.4",
         "consolidation/comments": "^1.0",
         "consolidation/config": "^1.0.0",
-        "consolidation/robo": "^1.4.10",
+        "consolidation/robo": "^1.4.12",
         "cweagans/composer-patches": "^1.6.5",
         "dealerdirect/phpcodesniffer-composer-installer": "^0.5.0",
         "dflydev/dot-access-data": "^1.1.0",
         "doctrine/common": "^2.5",
         "drupal/coder": "^8.3.1",
         "drupal/core": "^8.7.0",
         "drupol/phposinfo": "^1.6",
-        "drush/drush": "^9.5.0 || ^10.0.1",
+        "drush/drush": "^9.5.0 || ^10.2.2",
         "grasmash/drupal-security-warning": "^1.0.0",
         "grasmash/yaml-cli": "^1.0.0",
         "grasmash/yaml-expander": "^1.2.0",