try different syntax for python 2

Author: gstarovo

src/ecdsa/util.py

@@ -661,6 +661,7 @@ def sigdecode_der_ecdsa_sig_value(sig_der, order):
     r, rest = der.remove_integer(rs_strings)
     s, optional = der.remove_integer(rest)
     empty = optional
+    r_point = None
 
     # check if a is present
     if optional[:1] == b"\x02":
@@ -672,15 +673,17 @@ def sigdecode_der_ecdsa_sig_value(sig_der, order):
         r = der.integer_to_octet_string(r)
         # In point compression True is odd b"\x03", False is even b"\x02"
         if y:
-            r = b"\x03" + r
+            r_point = b"\x03" + r
         else:
-            r = b"\x02" + r
+            r_point = b"\x02" + r
     elif optional[:1] == b"\x04":
         y, empty = der.remove_octet_string(optional)
         r = der.integer_to_octet_string(r)
-        r = r + y
+        r_point = r + y
     if empty != b"":
         raise der.UnexpectedDER(
             "trailing junk after DER numbers: %s" % binascii.hexlify(empty)
         )
+    if r_point is not None:
+        return r_point, s
     return r, s