Delete pow.ethash and pow.ethash_utils

They were broken (lots of undefined names) and no longer used as
pyethash is now listed in requirements.txt

Author: gsalgado

ethereum/pow/__init__.py

@@ -1 +1 @@
-from ethereum.pow import chain, consensus, ethash, ethash_utils, ethpow
+from ethereum.pow import chain, consensus, ethpow

ethereum/pow/consensus.py

@@ -1,4 +1,4 @@
-from ethereum.pow import ethash, ethash_utils, ethpow
+from ethereum.pow import ethpow
 from ethereum import utils
 from ethereum.common import update_block_env_variables, calc_difficulty
 from ethereum.exceptions import VerificationFailed

ethereum/pow/ethash.py

@@ -1,12 +1,8 @@
-from ethereum.pow import ethash
 from ethereum import utils
-import time
 import sys
-import warnings
 from collections import OrderedDict
-from ethereum import utils
 from ethereum.slogging import get_logger
-import rlp
+import pyethash
 
 log = get_logger('eth.pow')
 
@@ -15,24 +11,10 @@
 else:
     from functools import lru_cache
 
-try:
-    import pyethash
-    ETHASH_LIB = 'pyethash'  # the C++ based implementation
-except ImportError:
-    ETHASH_LIB = 'ethash'
-    warnings.warn('using pure python implementation', ImportWarning)
-
-if ETHASH_LIB == 'ethash':
-    mkcache = ethash.mkcache
-    EPOCH_LENGTH = 30000
-    hashimoto_light = ethash.hashimoto_light
-elif ETHASH_LIB == 'pyethash':
-    mkcache = pyethash.mkcache_bytes
-    EPOCH_LENGTH = 30000
-    hashimoto_light = lambda s, c, h, n: \
-        pyethash.hashimoto_light(s, c, h, utils.big_endian_to_int(n))
-else:
-    raise Exception("invalid ethash library set")
+mkcache = pyethash.mkcache_bytes
+EPOCH_LENGTH = 30000
+def hashimoto_light(s, c, h, n):
+    return pyethash.hashimoto_light(s, c, h, utils.big_endian_to_int(n))
 
 TT64M1 = 2**64 - 1
 cache_seeds = ['\x00' * 32]
@@ -41,7 +23,6 @@
 
 
 def get_cache(block_number):
-    import sha3
     while len(cache_seeds) <= block_number // EPOCH_LENGTH:
         cache_seeds.append(utils.sha3(cache_seeds[-1]))
     seed = cache_seeds[block_number // EPOCH_LENGTH]
@@ -124,5 +105,3 @@ def mine(block_number, difficulty, mining_hash, start_nonce=0, rounds=1000):
             assert len(o[b"mix digest"]) == 32
             return bin_nonce, o[b"mix digest"]
     return None, None
-
-