Switch to my own images, with dependencies satisfied

Necessary PHP modules, as well as Composer, are provided in the new images: https://git.ethitter.com/docker/images/container_registry.

.gitlab-ci.yml

@@ -6,32 +6,9 @@ variables:
 cache:
   paths:
     - $HOME/.composer
+    - /root/.composer
 
 before_script:
-  # Install dependencies
-
-  # update the docker
-  - apt-get clean
-  - apt-get -yqq update
-
-  # install the required packages for the running CI tests
-  - |
-    apt-get -yqqf install lsb-release zip unzip subversion mysql-client libicu-dev libpng-dev libbz2-dev --fix-missing
-
-    if [[ $(lsb_release -a) =~ "stretch" ]]; then
-      apt-get -yqqf install default-libmysqlclient-dev --fix-missing
-    else
-      apt-get -yqqf install libmysqlclient-dev --fix-missing
-    fi
-
-  # PHP extensions
-  - docker-php-ext-install mbstring mysqli intl gd zip bz2
-
-  # Install Composer
-  - curl -sS https://getcomposer.org/installer | php
-  - mv composer.phar /usr/local/bin/composer
-  - export PATH="$HOME/.composer/vendor/bin:$PATH"
-
   # Set up WordPress tests
   - bash bin/install-wp-tests.sh $MYSQL_DATABASE root $MYSQL_ROOT_PASSWORD mysql latest true
 
@@ -48,17 +25,15 @@ before_script:
   - phpcs --config-set installed_paths $HOME/.composer/vendor/wp-coding-standards/wpcs,$HOME/.composer/vendor/automattic/vipwpcs
 
 PHPunit:PHP5.3:MySQL:
-  image: tetraweb/php:5.3
+  image: containers.ethitter.com:443/docker/images/php:5.3
   services:
     - mysql:5.6
   script:
     - phpcs -n
     - phpunit
-  when: manual
-  allow_failure: true
 
 PHPunit:PHP5.6:MySQL:
-  image: php:5.6-stretch
+  image: containers.ethitter.com:443/docker/images/php:5.6
   services:
     - mysql:5.6
   script:
@@ -66,7 +41,7 @@ PHPunit:PHP5.6:MySQL:
     - phpunit
 
 PHPunit:PHP7.0:MySQL:
-  image: php:7.0-stretch
+  image: containers.ethitter.com:443/docker/images/php:7.0
   services:
     - mysql:5.6
   script:
@@ -74,7 +49,7 @@ PHPunit:PHP7.0:MySQL:
     - phpunit
 
 PHPunit:PHP7.1:MySQL:
-  image: php:7.1-stretch
+  image: containers.ethitter.com:443/docker/images/php:7.1
   services:
     - mysql:5.6
   script:
@@ -82,7 +57,7 @@ PHPunit:PHP7.1:MySQL:
     - phpunit
 
 PHPunit:PHP7.2:MySQL:
-  image: php:7.2-stretch
+  image: containers.ethitter.com:443/docker/images/php:7.2
   services:
     - mysql:5.6
   script: