Update the tests (#4427)

* unpin the requirements and update all to latest available - needs more work still. see notes in `def host()`

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

* fix py3 monkey patch of testinfra docker using bash

Signed-off-by: Adam Hill <adam@diginc.us>

* update the other test files to use `host` instead of `Pihole`
Address some sticklr and codefactor
update python version from 3.7 to 3.8
preload `git` onto the centos/fedora test images, and switch which with command -v in the passthrough mock
testinfra is deprecated, use pytest-testinfra

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

Co-authored-by: Adam Hill <adam@diginc.us>

.github/workflows/test.yml

@@ -36,10 +36,10 @@ jobs:
       name: Checkout repository
       uses: actions/checkout@v2
     -
-      name: Set up Python 3.7
+      name: Set up Python 3.8
       uses: actions/setup-python@v2
       with:
-        python-version: 3.7
+        python-version: 3.8
     -
       name: Install dependencies
       run: pip install -r test/requirements.txt