bundle2: rename b2x:error:unknownpart to b2x:error:unsupportedcontent

This is a backward compatibility breakage per se. But bundle2 was explicitly
flagged as experimental, and this is one an error path anyway. So the worse
possible outcome from this change is to still have a crash but with a different
message.

mercurial/bundle2.py

@@ -828,9 +828,9 b' def handlereplycaps(op, inpart):'
     """Used to transmit abort error over the wire"""
     raise util.Abort(inpart.params['message'], hint=inpart.params.get('hint'))
 
-@parthandler('b2x:error:unknownpart')
+@parthandler('b2x:error:unsupportedcontent')
 def handlereplycaps(op, inpart):
-    """Used to transmit unknown part error over the wire"""
+    """Used to transmit unknown content error over the wire"""
     raise error.BundleValueError(inpart.params['parttype'])
 
 @parthandler('b2x:error:pushraced')

mercurial/wireproto.py

@@ -805,7 +805,8 b' def unbundle(repo, proto, heads):'
             os.unlink(tempname)
     except error.BundleValueError, exc:
             bundler = bundle2.bundle20(repo.ui)
-            bundler.newpart('B2X:ERROR:UNKNOWNPART', [('parttype', str(exc))])
+            errpart = bundler.newpart('B2X:ERROR:UNSUPPORTEDCONTENT')
+            errpart.addparam('parttype', str(exc))
             return streamres(bundler.getchunks())
     except util.Abort, inst:
         # The old code we moved used sys.stderr directly.