[SEBA-450] (part 2)

Add tox testing support on additional XOS library modules:

- xos-api
- xos-kafka (has no tests)
- xos-migrate (has no tests)
- xos-synchronizer

Change-Id: I98195bc9747971d3515882d517affe058dd86ac5
diff --git a/tox.ini b/tox.ini
index ea9ee50..2b634a9 100644
--- a/tox.ini
+++ b/tox.ini
@@ -15,7 +15,6 @@
 ; using tox.ini only to store config information for other tools
 
 [flake8]
-; F821, ignoring undefined names would be valuable, but our testing dynamically loads them
 ; W503, allow breaks before binary operators (see: https://github.com/PyCQA/pycodestyle/issues/498)
 ignore = W503
-max-line-length = 120
+max-line-length = 119