Add move_role

move_role will only send changed roles.
discord will accept trying to move to position 0, or trying to move the
everyone role. It will result in unexpected changes, so we prohibit it.

discord/client.py

@@ -2129,6 +2129,62 @@ class Client:
 
     # Role management
 
+    @asyncio.coroutine
+    def move_role(self, server, role, position):
+        """|coro|
+
+        Moves the specified :class:`Role` to the given position in the :class:`Server`.
+
+        This does **not** edit the role ordering in place.
+
+        Parameters
+        -----------
+        server : :class:`Server`
+            The server the role belongs to.
+        role : :class:`Role`
+            The role to edit.
+        position : int
+            The position to insert the role to.
+
+        Raises
+        -------
+        InvalidArgument
+            If position is 0, or role is server.default_role
+        Forbidden
+            You do not have permissions to change role order.
+        HTTPException
+            If moving the role failed, or you are of too low rank to move the role.
+        """
+
+        if position == 0:
+            raise InvalidArgument("Cannot move role to position 0")
+
+        if role == server.default_role:
+            raise InvalidArgument("Cannot move default role")
+
+        if role.position == position:
+            return  # Save discord the extra request.
+
+        url = '{0}/{1.id}/roles'.format(endpoints.SERVERS, server)
+
+        change_range = range(min(role.position, position), max(role.position, position) + 1)
+
+        roles = [r.id for r in sorted(filter(lambda x: (x.position in change_range) and x != role, server.roles), key=lambda x: x.position)]
+
+        if role.position > position:
+            roles.insert(0, role.id)
+        else:
+            roles.append(role.id)
+
+        payload = [{"id": z[0], "position": z[1]} for z in zip(roles, change_range)]
+
+        r = yield from self.session.patch(url, data=utils.to_json(payload), headers=self.headers)
+        log.debug(request_logging_format.format(method='PATCH', response=r))
+        yield from utils._verify_successful_response(r)
+
+        data = yield from r.json()
+        log.debug(request_success_log.format(json=payload, response=r, data=data))
+
     @asyncio.coroutine
     def edit_role(self, server, role, **fields):
         """|coro|