Setup warning configuration and document guidelines

setup.cfg

@@ -4,6 +4,36 @@ addopts=--tb=short --strict tests
 norecursedirs=.git _build tmp* requirements commands/*
 markers=
     cmd: Django admin commands.
+# https://docs.python.org/2/library/warnings.html#the-warnings-filter
+filterwarnings =
+    # Error by default
+    error
+    ## Deprecation related issues:
+    ## * Not clean:
+    ##   - default - in our own code till they are fixed (we can see what we
+    ##     need to fix, but builds don't break)
+    ##   - ignore - in other's code (no noise please, clean ours first)
+    ## * Clean:
+    ##   - error - in our own code (don't regress)
+    ##   - default - in other's code if they are not fixed.  Be specific about
+    ##     what module so we don't allow other brokenness in (able to watch
+    ##     others fixing their code, don't hide it)
+    ##   - error - if we have no occurances in our's or other's code (keep it
+    ##     clean - should essentially not be listed and falls to default error
+    ##     behaviour)
+    #
+    # Sadly can't use RemovedInDjango20Warning directly
+    # Not Clean
+    default:.*settings.MIDDLEWARE_CLASSES is deprecated.*
+    default:.*use_for_related_fields.*
+    # Clean
+    default:.*assignment_tag.*::.*socialaccount
+    ## Other
+    # allauth - these two are deprecated, unused in our code but trigger a
+    # false positive.  Likely because of Django template loader simply also
+    # loading the deprecated module.
+    ignore:.*account_tags.*
+    ignore:.*socialaccount_tags.*
 
 [pydocstyle]
 inherit=false