bundle2: raise BundleValueError error for stream level unsupported params

This ensures both consistency and smooth propagation over the wire.

mercurial/bundle2.py

@@ -523,7 +523,7 b' class unbundle20(unpackermixin):'
         if name[0].islower():
             self.ui.debug("ignoring unknown parameter %r\n" % name)
         else:
-            raise KeyError(name)
+            raise error.BundleValueError(params=(name,))
 
 
     def iterparts(self):

tests/test-bundle2.t

@@ -166,7 +166,7 b' Create an extension to test bundle2 API'
   >     unbundler = bundle2.unbundle20(ui, sys.stdin)
   >     try:
   >         params = unbundler.params
-  >     except KeyError, exc:
+  >     except error.BundleValueError, exc:
   >        raise util.Abort('unknown parameters: %s' % exc)
   >     ui.write('options count: %i\n' % len(params))
   >     for key in sorted(params):
@@ -304,7 +304,7 b' Test unknown mandatory option'
 ---------------------------------------------------
 
   $ hg bundle2 --param 'Gravity' | hg statbundle2
-  abort: unknown parameters: 'Gravity'
+  abort: unknown parameters: Stream Parameter - Gravity
   [255]
 
 Test debug output