bitcoin: avoid floating point in int_to_hex

electrum/bitcoin.py

@@ -60,7 +60,7 @@ def int_to_hex(i: int, length: int=1) -> str:
     if not isinstance(i, int):
         raise TypeError('{} instead of int'.format(i))
     range_size = pow(256, length)
-    if i < -range_size/2 or i >= range_size:
+    if i < -(range_size//2) or i >= range_size:
         raise OverflowError('cannot convert int {} to hex ({} bytes)'.format(i, length))
     if i < 0:
         # two's complement