[mypy] #163: verify: exit when failing to retrieve a chunk

Use urllib.error.HTTPError
Could fix #351, since 'None' (nothing) used to be returned
and the error was:
TypeError: 'NoneType' object is not subscriptable

silkaj/blocks.py

@@ -15,11 +15,11 @@
 
 import logging
 from typing import List
+from urllib.error import HTTPError
 
 from click import INT, argument, command, progressbar
 from duniterpy.api import bma
 from duniterpy.api.client import Client
-from duniterpy.api.errors import DuniterError
 from duniterpy.documents import Block
 
 from silkaj.constants import BMA_MAX_BLOCKS_CHUNK_SIZE
@@ -81,9 +81,11 @@ def get_chunk_size(
 
 def get_chunk(client: Client, chunk_size: int, chunk_from: int) -> List:
     try:
-        return client(bma.blockchain.blocks, chunk_size, chunk_from)
-    except DuniterError as error:
-        logging.error(error)
+        chunk = client(bma.blockchain.blocks, chunk_size, chunk_from)
+    except HTTPError as e:
+        logging.error(e)
+        message_exit("Error: Network error to get chunck")
+    return chunk
 
 
 def verify_block_signature(invalid_blocks_signatures: List[int], block: Block) -> None: