Add pytest warning filter for format_decimal deprecation

Author: akx

setup.cfg

@@ -6,6 +6,9 @@ norecursedirs = venv* .* _* scripts {args}
 doctest_optionflags = ELLIPSIS NORMALIZE_WHITESPACE ALLOW_UNICODE IGNORE_EXCEPTION_DETAIL
 markers =
     all_locales: parameterize test with all locales
+filterwarnings =
+    # The doctest for format_number would raise this, but we don't really want to see it.
+    ignore:babel.numbers.format_decimal:DeprecationWarning
 
 [bdist_wheel]
 universal = 1