Merge pull request #7077 from docker/dependabot/pip/ddt-1.2.2

Bump ddt from 1.2.0 to 1.2.2

requirements-dev.txt

@@ -1,5 +1,5 @@
 coverage==4.5.4
-ddt==1.2.0
+ddt==1.2.2
 flake8==3.7.9
 mock==3.0.5
 pytest==3.6.3