fix: decode error wording

tlslite/keyexchange.py

@@ -713,7 +713,9 @@ def makeServerKeyExchange(self, sigHash=None):
         ext_c = self.clientHello.getExtension(ExtensionType.ec_point_formats)
         ext_s = self.serverHello.getExtension(ExtensionType.ec_point_formats)
         if ext_c:
-            if ECPointFormat.uncompressed not in ext_c.formats:
+            if ext_c.formats == []:
+                raise TLSDecodeError("The compression list is empty.")
+            elif ECPointFormat.uncompressed not in ext_c.formats:
                 raise TLSIllegalParameterException(
                     "The client does not advertise "
                     "the uncompressed point format extension.")
@@ -1133,7 +1135,7 @@ def calc_shared_key(self, private, peer_share,
         except AssertionError:
             raise TLSIllegalParameterException("Invalid ECC point")
         except DecodeError:
-            raise TLSDecodeError("Unexpected error")
+            raise TLSDecodeError("Empty point format extension")
         if isinstance(private, ecdsa.keys.SigningKey):
             ecdh = ecdsa.ecdh.ECDH(curve=curve, private_key=private)
             ecdh.load_received_public_key_bytes(peer_share,