The validate method for a constraint only accepts the value being
verified. This is sufficient for most data checks (range, regex) and the
calls to one of the service clients. But it is limiting in the sense
that it prevents us from ever having constraints that span multiple
parameters (such as ensuring that two values are compatible).
What caused this is the atttempt to add a constraint to ensure a
parameter's value is a valid Heat resource type. To verify this, the
constraint code needs access to the resolved environment. I opted to
pass the entire template down instead to make things more flexible.
The call to the BaseCustomConstraint (which appears to be the entry
point for most plugins) will attempt to use the new signature with the
template, but will fall back to the original call for backward
compatibility.
Change-Id: I5dc94c964b35578e84da641278a4175a37038498
4fdf72b000