refactor(homestead): remove int() from calculate_block_difficulty (#1415)

src/ethereum/forks/homestead/fork.py

@@ -765,21 +765,21 @@ def calculate_block_difficulty(
         Computed difficulty for a block.
     """
     offset = (
-        int(parent_difficulty)
-        // 2048
-        * max(1 - int(block_timestamp - parent_timestamp) // 10, -99)
+        parent_difficulty
+        // Uint(2048)
+        * max(1 - (block_timestamp - parent_timestamp) // U256(10), -99)
     )
-    difficulty = int(parent_difficulty) + offset
+    difficulty = parent_difficulty + offset
     # Historical Note: The difficulty bomb was not present in Ethereum at the
     # start of Frontier, but was added shortly after launch. However since the
     # bomb has no effect prior to block 200000 we pretend it existed from
     # genesis.
     # See https://github.com/ethereum/go-ethereum/pull/1588
-    num_bomb_periods = (int(block_number) // 100000) - 2
+    num_bomb_periods = (block_number // Uint(100000)) - 2
     if num_bomb_periods >= 0:
         difficulty += 2**num_bomb_periods
 
     # Some clients raise the difficulty to `MINIMUM_DIFFICULTY` prior to adding
     # the bomb. This bug does not matter because the difficulty is always much
     # greater than `MINIMUM_DIFFICULTY` on Mainnet.
-    return Uint(max(difficulty, int(MINIMUM_DIFFICULTY)))
+    return Uint(max(difficulty, MINIMUM_DIFFICULTY))