XSPEC: fix up error message

The error message that happens in the rare case of the XSPEC model
failing now

a) correctly lists the parameters and their values

   previously the parameters were being mapped to the low-energy
   axis, which is obviously garbage

b) any keyword arguments are now also included in the error
   message

The energy grid could be included, but this is something the caller
can more-easily identify than a particular set of parameters (and
keyword argyments) so it's not worth adding to the already-long
line.

sherpa/astro/xspec/__init__.py

@@ -1433,11 +1433,17 @@ def calc(self, p, *args, **kwargs):
             #   - model class
             #   - model name
             #   - parameter list
+            #   - any kwargs
             #
             msg = f"{ve}: {self.type}.{self.name}"
-            for par, val in zip(self.pars, args[0]):
+            for par, val in zip(self.pars, p):
                 msg += f" {par.name}={val}"
 
+            if kwargs:
+                msg += " KEYWORDS "
+                for k, v in kwargs.items():
+                    msg += f"{k}={v}"
+
             raise ValueError(msg) from None
 
         # This check is being skipped in the 4.8.0 release as it