MAINT - Update tests to comply with flake8 W504

This commit updates to comply with the style of [flake8 rule W504](PyCQA/pycodestyle#502)
where previously this code was styled to comply with [flake8 rule W503](https://lintlyci.github.io/Flake8Rules/rules/W503.html)
which has fallen out of favor. W503 is set to be ignored

(cherry picked from commit 0fe98e1)

.flake8

@@ -1,5 +1,5 @@
 [flake8]
-ignore = E501
+ignore = E501,W503
 pytest_mark1 = name=test_id
                value_match=uuid
                enforce_unique_value=true

.travis.yml

@@ -5,4 +5,4 @@ python:
 install:
   pip install -r requirements.txt
 script:
-  flake8 --ignore E501
+  flake8 --ignore E501,W503

molecule/default/tests/test_hypervisor_free.py

@@ -70,7 +70,7 @@ def test_hypervisor_free(host):
     assert "vcpus" in stats
     assert "vcpus_used" in stats
     assert "free_disk_gb" in stats
-    assert ((stats['memory_mb']) * ram_ratio -
-            (stats['memory_mb_used'])) / 1024 > 0
+    assert ((stats['memory_mb']) * ram_ratio
+            - (stats['memory_mb_used'])) / 1024 > 0
     assert (stats['vcpus'] * cpu_ratio - stats['vcpus_used']) > 0
     assert (stats['free_disk_gb'] * disk_ratio) > 0