* invalid character '$' looking for beginning of value

[dansimau]

When diffing policy output that is not valid JSON, we see errors like:

* invalid character '$' looking for beginning of value

This happens, for example, when one of the lines looks like this:

assume_role_policy:                                       "{\"Version\":\"2012-10-17\",\"Statement\":[{\"Sid\":\"\",\"Effect\":\"Allow\",\"Principal\":{\"AWS\":[\"arn:aws:iam::XXXXXX:user/foo\"]},\"Action\":\"sts:AssumeRole\"}]}" => "${var.assume_role_policy}"

In this case, there is no unified diff. The problem is that the indenting is implemented by using json.Indent which bubbles up the error if the indenting fails.