feat(py3/py27): integrate pytest-html

In addition to gitlab integration, this one provides quite additional feature:

• display captured stdout/stderr which can been needed for debugging
• is present for everyjob while gitlab integration is only for the MR
• I find the output more useful (because more information) and easier to use that gitlab no so great UI (but less easy to reach)
• it's pretty much free to add

README.md

@@ -24,7 +24,7 @@
 stages:
   # put your testing/linting stages here before
   # for build-debian-package.yml
-  - build-debian
+  - build-debian-package
   - upload-deb-to-heptapod
   # for build-docker-image.yml
   # for release-on-heptapod.yml