[wip] 1211 mariadb compatibility (#1440)

fixes #1211 

As we've already upgraded our minimum requirement to 7.1 there's no current need to force a constraint on dbal 2.7+.

framework/core/phpunit.xml

@@ -19,4 +19,9 @@
             <exclude>./tests/Install</exclude>
         </testsuite>
     </testsuites>
+    <filter>
+        <whitelist processUncoveredFilesFromWhitelist="true">
+            <directory suffix=".php">./src/</directory>
+        </whitelist>
+    </filter>
 </phpunit>