allow "members" property to be absent

Closes-Bug: #1235904
Change-Id: If18f6d386d07ee65ce54f8372ad646864b486303
Signed-off-by: Stephen Gran <stephen.gran@guardian.co.uk>
HOT str_replace default to empty string for param

If a str_replace param cannot be resolved or is None,
substitute an empty string in order to prevent raising
an exception during validate.

Closes Bug: #1234390
Change-Id: Ica6b84cfc2157b4e1f561f737e9aa67b9f6018ca
Merge "HOT str_replace default to empty string for param" into milestone-proposed
Merge "allow "members" property to be absent" into milestone-proposed