Include double quotes for environment variables

Co-Authored-By: Javier Casares <javier@casares.org>

Author: desrosj

.env.default

@@ -12,25 +12,25 @@
 ###
 
 # Path to the directory where files can be prepared before being delivered to the environment.
-export WPT_PREPARE_DIR=/tmp/wp-test-runner
+export WPT_PREPARE_DIR="/tmp/wp-test-runner"
 
 # Path to the directory where the WordPress develop checkout can be placed and tests can be run.
 # When running tests in the same environment, set WPT_TEST_DIR to WPT_PREPARE_DIR
-export WPT_TEST_DIR=wp-test-runner
+export WPT_TEST_DIR="wp-test-runner"
 
 # API key to authenticate with the reporting service in 'username:password' format.
-export WPT_REPORT_API_KEY=
+export WPT_REPORT_API_KEY=""
 
 # (Optionally) define an alternate reporting URL
-export WPT_REPORT_URL=
+export WPT_REPORT_URL=""
 
 # Credentials for a database that can be written to and reset.
 # WARNING!!! This database will be destroyed between tests. Only use safe database credentials.
 # Please note that you must escape _or_ refrain from using # as special character in your credentials.
-export WPT_DB_NAME=
-export WPT_DB_USER=
-export WPT_DB_PASSWORD=
-export WPT_DB_HOST=
+export WPT_DB_NAME=""
+export WPT_DB_USER=""
+export WPT_DB_PASSWORD=""
+export WPT_DB_HOST=""
 
 # (Optionally) set a custom table prefix to permit concurrency against the same database.
 export WPT_TABLE_PREFIX=${WPT_TABLE_PREFIX-wptests_}
@@ -40,26 +40,26 @@ export WPT_PHP_EXECUTABLE=${WPT_PHP_EXECUTABLE-php}
 
 # (Optionally) define the PHPUnit command execution call.
 # Use if `php phpunit.phar` can't be called directly for some reason.
-export WPT_PHPUNIT_CMD=
+export WPT_PHPUNIT_CMD=""
 
 # (Optionally) define the command execution to remove the test directory
 # Use if `rm -r` can't be called directly for some reason.
-export WPT_RM_TEST_DIR_CMD=
+export WPT_RM_TEST_DIR_CMD=""
 
 # SSH connection string (can also be an alias).
 # Leave empty if tests are meant to run in the same environment.
-export WPT_SSH_CONNECT=
+export WPT_SSH_CONNECT=""
 
 # Any options to be passed to the SSH connection
 # Defaults to '-o StrictHostKeyChecking=no'
-export WPT_SSH_OPTIONS=
+export WPT_SSH_OPTIONS=""
 
 # SSH private key, base64 encoded.
-export WPT_SSH_PRIVATE_KEY_BASE64=
+export WPT_SSH_PRIVATE_KEY_BASE64=""
 
 # Output logging
 # Use 'verbose' to increase verbosity
-export WPT_DEBUG=
+export WPT_DEBUG=""
 
 # Certificate validation
 # Use 1 to validate, and 0 to not validate