Add tests for MCPServer.read_resource exception handling

Cover the two exception paths in read_resource that were previously
excluded from coverage: unknown resource errors and resource read
failures. The tests verify that both cases properly raise MCPError
with appropriate messages.

Also improve exception chaining by using 'from exc' syntax and
simplify the error message format.

Author: Kludex

src/mcp/server/lowlevel/server.py

@@ -795,12 +795,7 @@ async def _handle_request(
 
             await message.respond(response)
         else:  # pragma: no cover
-            await message.respond(
-                types.ErrorData(
-                    code=types.METHOD_NOT_FOUND,
-                    message="Method not found",
-                )
-            )
+            await message.respond(types.ErrorData(code=types.METHOD_NOT_FOUND, message="Method not found"))
 
         logger.debug("Response sent")
 

src/mcp/server/mcpserver/server.py

@@ -348,15 +348,14 @@ async def read_resource(self, uri: AnyUrl | str) -> Iterable[ReadResourceContent
 
         context = self.get_context()
         resource = await self._resource_manager.get_resource(uri, context=context)
-        if not resource:  # pragma: no cover
+        if not resource:
             raise ResourceError(f"Unknown resource: {uri}")
 
         try:
             content = await resource.read()
             return [ReadResourceContents(content=content, mime_type=resource.mime_type, meta=resource.meta)]
-        except Exception as e:  # pragma: no cover
-            logger.exception(f"Error reading resource {uri}")
-            raise ResourceError(str(e))
+        except Exception as exc:
+            raise ResourceError(f"Error reading resource {uri}") from exc
 
     def add_tool(
         self,