Use sys.exit(...) instead of exit(...): exit(...) should not be used in programs

contrib/linearize/linearize-hashes.py

@@ -87,7 +87,7 @@ def get_block_hashes(settings, max_blocks_per_call=10000):
 		for x,resp_obj in enumerate(reply):
 			if rpc.response_is_error(resp_obj):
 				print('JSON-RPC: error at height', height+x, ': ', resp_obj['error'], file=sys.stderr)
-				exit(1)
+				sys.exit(1)
 			assert(resp_obj['id'] == x) # assume replies are in-sequence
 			if settings['rev_hash_bytes'] == 'true':
 				resp_obj['result'] = hex_switchEndian(resp_obj['result'])