[fix] #58 fix challenge uuid string format

duniterpy/documents/ws2p/messages.py

 import json
-import uuid
+
 from typing import Optional
 
 from duniterpy.documents import Document
 from duniterpy.key import VerifyingKey, SigningKey
+from duniterpy.helpers import get_ws2p_challenge
 
 
 class Connect(Document):
@@ -25,7 +26,7 @@ class Connect(Document):
         self.pubkey = pubkey
         if challenge is None:
             # create challenge
-            self.challenge = uuid.uuid4().hex + uuid.uuid4().hex
+            self.challenge = get_ws2p_challenge()
         else:
             self.challenge = challenge
         # add and verify signature
@@ -71,7 +72,7 @@ class Ack(Document):
     def __init__(self, currency: str, pubkey: str, challenge: str,
                  signature: Optional[str] = None) -> None:
         """
-        Init Connect message document
+        Init Ack message document
 
         :param currency: Name of currency
         :param pubkey: Public key of node
@@ -124,7 +125,7 @@ class Ok(Document):
     def __init__(self, currency: str, pubkey: str, challenge: str,
                  signature: Optional[str] = None) -> None:
         """
-        Init Connect message document
+        Init Ok message document
 
         :param currency: Name of currency
         :param pubkey: Public key of node

duniterpy/tools.py

+import uuid
 from typing import Union
 from libnacl.encode import hex_decode, hex_encode
 
@@ -60,3 +61,12 @@ def convert_seed_to_seedhex(seed: bytes) -> str:
     :rtype str:
     """
     return hex_encode(seed).decode("utf-8")
+
+
+def get_ws2p_challenge() -> str:
+    """
+    Return two uuid v4 concatened as ws2p challenge
+
+    :rtype str:
+    """
+    return str(uuid.uuid4()) + str(uuid.uuid4())